Possibility of having A-Check at other airport than one's base has been suggested before, but here's an idea how to do it more realistic:
1. A-check would be possible only at airports where airline with same fleet type is based. For example, if I wanted to do A-Check on B737NG, I would have to do it on airport where some B737NG is based by some airline (= presuming they have maintenance facility for such fleet).
2. Doing A-Check out of base would be more pricey. Difference between "standard" A-check and out-of-base A-Check would be income of airline that would rent this maintenance facility.
3. Airline could set price for such service, therefore creating competition between airlines on large airports. On certain markets, price of such service would be capped (airline couldn't charge more than XX$ to prevent them from blocking competition), while on some this would be unlimited (for example, USSR-based airlines could set incredibly high price for such service - but only until there would be competitor who would set better price). Price could be different (presumably cheaper) for alliance partners.
This would bring new elements:
- More scheduling options
- Possibility of new income for airlines
- New advantage of being in alliance (and perhaps need to take more time considering which airline to invite)
- Some new twists into the game - for example if my "maintenance partner" close particular fleet, I will need to reschedule within given time as he will no longer be able to perform maintenance for me
- More cooperation and relationships between airlines, adding new dimension to the game