When changing a livery of an already owned plane it shouldnt be instant, rather the plane should be flown to a maintenance base or airport with adequate facilites for a few hours. What i mean by adequate facilities is there are many airports which arent really considered maintenace bases but do have painting facilities. Two massive ones in Europe (that i know of) are Dublin and Rome FCO.
So basically a closer to IRL system. Also when having your own hangars is eventually implemented, they could drastically shorten repaint time.
Maintenace should be longer. Probably an unpopular opinion . I recently did my first maintenace check on a 787 based in BRI. Plane flew of to FRA and came back within like 4 hours max (wasnt couting exactly, info could be a bit off). I think this is a bit too unrealistick. It should at least be out of action in FRA for like 12-14 hours.
*im not yet aware of timing for S, M and X planes, but im guessing its a similar story
We should be able to choose where we send airplanes for maintenace and that choice should have different effects. Ill just use the example of British and i think also Qantas. They do not do heavy maintenance in house, but send their planes to Manila in the Philipines to undergo heavy maintenance checks. As a matter of fact one or two A380s are doing this exact thing IRL even during the coronavirus crisis. The effects i was talking about could be for example: if i choose to send my plane to a nearby base, maintenance lasts less time and costs more, maybe i send my plane to a far away base, for slower but cheaper maintenance and etc…
These arent really feature proposals, just hope to hear some of your thoughts on this and any possible improvements to the above mentioned ideas!