To place a VF you MUST have a Radar. To place a Repair Pad you MUST have a VF. All other buildings can be placed at will. (Refs ofc only on resource nodes) Reasonings: Delays Rushes and gets research started earlier. If you don't have a VF you either have no vehicles or fucked up bad. You either don't need or don't deserve a repair pad.
Just a thought, but sometimes it isn't even about rushing, an early vf means securing much more ground then the opponent if they choose a radar first, or being able to reinforce a point with an apc if you lose the rax. Both are very important things to consider, especially the apc considering wages means your radar doesn't really get delayed at all. Even being able to get a jeep to quickly get to ref points is a big deal, one that I don't see get used enough. Not to say I wouldn't mind such a change, I rather like the slow start of rounds when there's no vehicles, but you do lose a ton of options and strategies that don't revolve around rushing the enemy team.
But, having a possibility to have early VF can also make it easier to have games unbalanced right from the start. Especially public games. So IMO its a factor which can contribute to big advantages right from the start and can make even bigger difference in balance if one team is just a little bit worse, if you know what I mean. So I somewhat like this idea.