Tabletop Version of Nintendo's Super Smash Bros.

You already have modifiers based on a character's size. Will attacks also have modifiers?

For example, if a Heavy character hits a Light character, does the target suffer more knockback, regardless of their current health level? Does being a Light character prevent some or all knockback damage against Heavy characters, depending on the condition of the Heavy character?

Going with your card idea (and with the limited knowledge and play experience I have with SSB on my old N64 I think), could you have some weapons that cause variable damage and/or knockback, or damage INSTEAD of knockback (and vice versa)? I imagine a huge hammer, for example, that causes damage + knockback against Medium and Heavy characters, but only causes damage against Light characters, since it's more like squashing a bug than smacking someone baseball-bat-style.

Please share your thoughts. Best of success with your game. :)

Some arenas in Smash Brothers behave in wildly different ways. If you can figure out a way to represent that on a board or through cards(such as events that make terrain fall away and whatnot), then you could expand the game with a new arena(s) and characters in one box or in a pack.

I don't think this would work very well when you factor in movement because too many effects would whiff in the air.

Better to have a MtG type system with abilities that could be played on any turn(basic attacks, jump moves, etc), and then abilities that could only be played on your turn(Charge up attacks)

Maybe it was in the N64 version(I can't remember), but the latest versions I played damage depended on the skill. Easiest reference would be Samus' charge up blast.

Not sure if I would use dice on the return-to-board mechanic. I think too many people would roll poorly and basically die on an otherwise recoverable hit. Your characters should have the standard jump + double jump + aerial move(I think that was generally all you had) found in the game. They get knocked 10 spaces off the board, the jump for say X, double jump for Y more, and use their aerial move for whatever range/ability that move has. Each of those 3 moves could have a cooldown that only resets when the player touches the board or some other physical object. I have had games where another guy gets thrown in my direction and I use him as a stepping stone to get back on land, which is usually pretty epic.

Turned based combat will definitely slow things down, so it is something you will have to consider designing around. Ways to make players take their actions quickly and whatnot.

You may have to take into account that the last player to go may get ganged up on which is why I would suggest some instant type abilities that he can perform on his turn to defend himself, or otherwise inject himself into a battle happening between other players.

Instant and Sorcery. Each player has abilities that can either be played on their turn, or on anyone's turn.

Quick abilities, basic attacks, etc could be used at any time while slower abilities, charge-up attacks, etc could only be used on their turn.

The only problem you might have is if you use a cooldown system then other players will know what abilities you have that are ready to go. Not that they don't know this in the video game, but the faster pace doesn't let them think about this as much as in a turn-based game.

Using a draw based system would allow you to keep information hidden and therefore surprise your enemies with certain moves, but you lose some ability to handle skills like the video game does.

Given how important jumping and movement is in the game, you might keep the 3 jump moves on the board where you can use cooldowns, while the rest of your abilities are drawn each turn.

You wouldn't have to use "decks". I think 10 or fewer cards per player would work pretty well on a draw system.

I am not sure how you would capture the breadth of character abilities found in the video game on one character card, especially including stats and text outlining how each move is supposed to hit enemies, unless that card happened to be extra large.

For instance, with Samus you might represent each of these lines as 1 card:
Jumps + Aerial Move
Basic attacks - Kicks, Sweeps, Punches, etc
Grabs
Energy Cannon
Bomb Ball
Energy Whip (Aerial Move)
Flamethrower
Missile
Homing Missile
Morph (Plus all Morph abilities)

I am thinking that if you use 1 card with the character info and as many abilities as you can fit on the card, you will have a character that has maybe 2-3 moves they get to spam repeatedly.

One card might look like this:

Energy Canon
Deals X% damage per turn charged. (Y turns max)
Charge can be interrupted.
Travels horizontally Z spaces per turn until striking a player or obstacle.

There are some things that I've been thinking about making a fighting game into a board game:

The relentless nature of fighting game would suggest to ditch the basic IGOUGO turn based and use some sort of reaction based system.

Mixups; are situations where an opponent forces the other in a bad spot where he has to essentially guess his next move, this is something that is easy to incorporate into a board game (by making them guess, or course) and are frequent in any fighting game.

Invincibility frames and Hitboxes; are essentially the things that tell which move beats the other when performed at the same time, this and many other nuances are pretty hard to implement in a board game. (I had some sort of token system in mind where players secretly choose a number between 1-5 representing the the distance and precise timing. Some moves would be strong in some areas, while completely missing in others. This of course would be guesswork too, like in the mixup situations, so I don't really know).

Blocking and Safety of the moves; in short when an "unsafe" move is blocked, it opens the attacker up for unopposed counterattack. Unsafe moves usually are more powerful in other areas. Blocking of course would be a reaction as normal (and as in Smash Bros., would be a used resource).

Well, these are some things to consider, and maybe get inspiration from.
There would be some more things to consider when trying to emulate a fighting game, but I think the more one tries to emulate one, more dull the end result would be.

Platforming and 2d:
First question is are you looking for the game to take place on a 2d plane like smash bros? Sticking with your miniature based theme I would also question platform design. Because in smash bros you will often find yourself on a different platform maybe even directly on top of your opponent.

Jumping:
Jumping is a critical component of smash bros. it seems like you will have to simulate the double jump and special jump mechanism. Rolling dice to live is a horrible idea, but I also feel that getting hit at 100 percent is certain death.

Items, item throwing and blocking:
Another key component. Items could offer special abilities with limited uses. But throwing the item is a super fun aspect of people trying to recover from a knock off. Not to mention it opens up the possibility of a preemptive knock off. Blocking is the hardest because it's a reactive action. But so is dodging. Again this is a key component because it burns your ability to maneuver.

Of course I am trying to come as close as possible here trying to simulate the game and that might not be optimal for the board version.

My gut says that if your intent is to use miniatures, I would also assume an action point allowance system is applicable. And I would propose a way to gain additional action points by standing still. But the maximum action point spending should be based on jumping back to the platform. But there needs to be some element of simultaneous movement. Someone's suggestion of instants from magic is a fantastic idea... Except maybe instead of cards you build a magic-like stack based on action points spending. Of course not all points can be spent on the stack but reactive points should steal from your ability to maneuver.

You have a solid start here. I would like to see it blossom.