Vehicle system is and will be a problem

On most high pop servers, vehicles is or will be a problem. They are spawned even if the person isn't online for 2-3 days.
The idea of spawning every vehicle where they were is nice but on the side of the optimisation, it's terrible. Spawning a vehicle when the player is offline is, atm, useless.
(Except if the player's team want to use it...).
If we add to that the number of constructions on the map (3500+ objects on our server in a week) and vehicle spawned by the server, it becomes a major issue on long term for server with high pop.

Here are some screenshots of a safezone, to illustrate my point
<img src="http://i.imgur.com/EYGLslh.png/>
<img src="http://i.imgur.com/tRBTrY6.jpg/>
<img src="http://i.imgur.com/9dyuDc6.jpg/>

On every server with whatever rates, the amount of vehicle, constructions,  will sooner of later become a problem.
We don't want to be forced to wipe for this reason..


Here are some ideas possible solutions :
- Automatic building decay (If owner is not around x days)
- max of x buildings parts per player
- Garage system (Garages at safe zone + "portable garage" craftable, like a box that players can build in their bases)
<img src="http://i.imgur.com/gsdQlY8.png/>
- Not spawn all vehicle at server start but spawn x vehicles around players each y minuts with a total of k vehicles