Anyone create military sims?

You are placing the cart in front of the horse.

Start with defining what sort of game you are making.

target audience?
complexity level?
playing time?
price range?

What might work for one type of game, will be completely out of place for the other. Unless you know what exactly it is you are trying to achieve, you risk ending up with a random mess of mechanisms which do not go well with one another.

There are many WW2/Historical wargames that simply use tiles and/or maps with terrain features printed on them. See Heroes of Normadie as a good example of this (they even use the top-down image printed tiles for units instead of minis)

This makes them more economical (which in the price range you're thinking of is required) and easy to set-up, store and transport; but less attractive as they're just flat boards placed on the tabletop.

You could look into 3D terrain (3d printed, molded plastics, laser-cut MDF, etc) but then the costs skyrocket accordingly.

Ultimately it comes down to two things;
1. Price
2. Appearance/Personal Preference

HOWEVER, before even thinking about this, you should have the mechanics of the game (actual game play) nailed down first. Design and appearance issues come after. Until you have your game fleshed out, just use pieces of paper with things scribbled on them in pen/pencil. It will be affordable and easy to change and update as required until you're satisfied with it.

Yes templates are fine for most purposes

What scale? Like 1/72, 1/300?

If you're going for *cities* being part of the battlefield, I'm guessing you're going with 1/300, otherwise you get a huge difference in scale between minis and terrain.

You don't need to make your own minis. There are a HUGE number of companies out there that produce miniatures for wargames and you can just make the rule system that players can use their preferred minis for. If your game stands out, a lot of players who already have miniatures could try them just with getting your the rulebook.

Same applies to terrain if you wanted to have rules for 3d terrain, lots of suppliers of wargames terrain of all scales out there.
(and a lot of my early wargame experience involved using books and random boxes (often the boxes I packed my minis in) for terrain)

The hard part is the "If your game stands out" part. There's a lot of wargame systems, some of which are very good. I like Stargrunt (by Ground Zero Games), it's nominally a sci-fi systems but it's built to be adaptable to any tech level. I haven't played WW2 tank games for many years, I'm generally more into sci-fi.

Phew. WWII tanks, eh? That's a crowded field. You have Flames of War, Bolt Action, Tanks, and a few others. Some of these are startlingly popular too with dedicated followings who dropped playing Warhammer seemingly out of left field in favor of them. They are stocked heavily at most FLGS I've been to. And that's not to mention the increasingly popular Weird War 2 market, Team Yankee, and then all of the sci-fi tank battle games, like Dystopian Wars and Dropship Commander. It needs to be a killer game to get attention these days.

This has already been mentioned, but $30 for a starter doesn't leave much room for including miniatures. To give you an idea, $100 gets you a Flames of War starter with:

1 Flames of War Mini Rulebook
1 Bridge at Remagen Army Book
1 Armored Rifle Platoon
3 M26 Pershing Tanks
5 M4A3 Sherman Tanks

All minis are 5mm, unpainted, plastic. If it is like most wargames, it's a $300 investment to build a viable force.

You should check out some of these games to get an idea of how they handle the problems you mentioned, why they are so popular (particularly Flames of War), and what you could do better.