Yeah, would be great !
Your idea is great !
Planner don’t really need to change, GA stands just need to appear on it, with a different color of course.
Also requirement should change depending on both the type of charter flight and the aircraft size.
I mean for a private lease I don’t think anything additional than the actual base ingame GA aerodrome is needed, while those from charter company would require ramp agent, service car and security, and cargo one should require some logistic infrastructure.
While charter or not, a small cessna shouldn’t need concrete/asphalt, but really aircraft compatibility in general.
As for military and private/corporate jet they should only be GA as they are owned and non “rented” and not commercially used.
The density of aircraft size/type on charter flights should match real life, and there should be no upper limit on aircraft size, only just they are (probably in real life) rarer than medium or smaller ones.
Also depending on the type of charter, some like the charter company operated have first class seat removed, but for a personally rented one should have normal seats or even be fitted with more luxurious seats, changing greatly the passenger density in both cases.
In France, when we talk about charter flight, most peoples probably only think about low cost flight of medium aircraft, and probably ignore this can also be renting an aircraft, and to be honest I also did not knew that prior to your post (which is why I needed to learn about it to be able to answer you, and even there the info are pretty vague).
I don’t know if commercially used charter do pass through a terminal, but private ones don’t, you just pass through the security checkpoint (no search seem to be performed from what I saw) and you directly arrive by car next to your aircraft, if you hired a pilot, it already have engines running (for jet at least) and ready to taxi.
And for being realistic, commercial charter flight should appear late on our planning.