The campaign...
1. I about having fun with XWM in a different way (cooperative play, rather than competitive play- making it competitive is really missing the point)
2. Is an opportunity to try new combinations of ships, pilots and upgrades that the standard game would either ...
a) not allow or...
b) not reward due to being less than optimally efficient
3. Is "fluff"-based, not just "game"-based, ie. there is an attempt to create something akin to the SW universe, not just a stand-alone game, so...
4. The cost to change ships could be seen as a way to acknowledge the fact that having a fleet of many different ship types in one squadron is a logistical nightmare, thus there is a cost for flying something seen as "non-standard" or "in limited supply". Yes, A-wings are now canon pre- Battle of Yavin (so are Z-95s) but by the time period of the HotAC campaign are now in more limited use or are in this sector of space...
5. It is all unofficial, so do what you want with it. Personally, I am o-k with it and see no reason to change. 5 exp, after all, is not really that much, once you are PS4+, where leveling up only increases the difficulty level of the game. Chnage it if you feel you must but whatever you do...
Have FUN.