I'm kind of against this, for two main reasons.
The first is that generally, if you capture an opponent's vehicle, it'll take some damage in the process. So, for example, if you toss a 'nade at it and then kill the driver, although you've done all the hard work in actually getting the thing, you get penalised whilst they didn't have any problems. This creates an awkward situation where, in attempting to capture vehicles, players are going to have to avoid trying to damage the thing, which is very unfair.
The second is that Spartans don't suffer any penalties for suffering damage - a Spartan with a single remaining point of Health is just as agile, accurate, and powerful as one without any damage whatsoever. Put simply, this would need to change as well, as there shouldn't be a double standard for vehicles and infantry.
That said, this could potentially make for fun Custom Game types, if you can spawn vehicles in pre-damaged or whatever, so I wouldn't mind it being included there. I just don't think it should be in Matchmaking.