Static encounters in a Combat based game

I ran into exactly this situation, and addressed it by making the static encounter... player vs player!
For reference, I was using a magic-based combat system that involved Spells and Items (which came in two different decks.)
The idea was that the player on the left of the active player* drew the encounter card. If a combat was involved, it told that player to set aside their "actual" hand (the one they were playing with for their character) and instead draw X spells and X items.
The combat was then resolved using the regular rules. Obviously it was different to a normal PvP encounter because the cards were more random, but otoh it meant that players could learn the strengths weaknesses of their opponents which made the static encounters more dangerous as the game went on.

*it wasn't always the player on the left who was the opponent - something else that it has in common with Starfarers. In fact, my system was developed independently but there are only so many variations you can use!)

I, too, tend to use idle players to act as the brains of "NPC" encounters. While using a generally weaker combatant, the player who gets to play the "encounter foe" can be more forward and take more chances, since they risk nothing themselves. This is also a good way to let players use exotic abilities that would be too unbalancing if given to an actual player.

I like to have some other token move around the table, which designates who controls the next static encounter. Once you run an encounter, you pass the token to your left, and the next player runs the next encounter. If you hold the encounter on your own turn, you pass it to your right, so that after your turn, you get the counter back, to use yourself. Particular players ae known to be more effective in running these NPC's and so the tension increases when they hold the token. Good stuff!

This sort of thing is a great way to lessen downtime.

the game has to be fun.

strategy for player vs player, intense competitive battles where
win, loose, can be determind.

but when playing against random monsters it can be outlandish
and fun. Nothing would make me more upset than to die here.

so go ahead let me fight 500 goblins just for experience points,
or face 3 adult red dragons, why not? crazy stuff, and since this
fight is more for collecting stuff, and gaining cool stuff,
if I'm about to loose, let me pay off the game master to
not let me die.
I may eat up a lot of cash but I can do crazy stuff that I can't do
in player vs player.

Here's an idea - give your static fighters a 'technique'. Their technique is represented by say 3-8 separate sequences of predetermined moves, with each sequence being say a few moves long. Each such sequence is recorded on a 'technique' card, with each move being listed one the card from top to bottom.

The player fighting the NPC begins by randomly selecting one face down NPC technique card and placing it in an opaque sleeve.

Then the fight begins.

(1) Player selects his attack.
(2) Player moves the sleeve containing the NPC moves down one notch to reveal NPC attack.
(3) Resolve outcome.
(4) Repeat from (1), unless NPC technique card is exhausted, in which case remove technique card from sleeve, return to NPC technique deck and shuffle. Select new technique card, place into sleeve then repeat from (1).

* powerful NPC opponents get more technique cards, making their likely form of attack harder to learn.
* players learn the techniques of NPC opponents just like they would in real life, but it's harder to predict the technique of powerful opponents, and easier to predict what unskilled opponents will do.
* no need to use idle players

The pre-programmed fight sequence was actually inspired by two concepts, firstly the idea of a computer program (yes I do various types of programming for my day job), and by a computer game called corewar, in which players create very simple computer programs which run together on an abstract CPU with the aim of incapacitating the enemy program by sending it into an endless loop or making it jump to an illegal memory address. I think there was also a board game called battlebots that used these ideas of pre-programmed sequences.

A powerful extension to the pre-programmed technique idea used in corewar is the ability to add conditional statements into the sequence. For our example, this would mean something like , IF hit points drop below N OR fatigue climbs above M, SWITCH to technique C.

If this mechanic could be implemented for a card game (and I think that with some thought it could be) then rather than have two players slugging it out with the very familiar mechanic of simultaneous action selection, you can have players 'design' a fighters technique and then let him or her loose against an opponent designed by another player.

I think it makes for a fun game if some control is removed from the player, and moved into an upfront 'planning' stage. It would also be superb for tournament and online play.

Thinking about it, an pre-prepared action board may be better than cards if using this scheme. Cards could still be used to represent weapons, or possibly used by players to 'intervene' in the pre-programmed sequence when their fighter needs a hint.