I suggest for TH300 idea that diminishing returns be used, so (to uses bonus as an example), the first RCC would add 10%, a second one built would only add 5% bonus, the third 3%, and so on. This way there wouldn't be a mad rush to build more RCC than the other player, as having 6 vs his 5 would not benefit you as much as your 2 vs his 1.
Here is another alternative. I do think there should be some kind of limit on the units built, but it shouldn't be the hard limit found in SC. In theory the player can build as many vehicles as they want, but once the player passes the capacity of the RCC the effectiveness of the unit starts to degrade in a logarithmic curve, somewhat opposite of the diminishing return above.
Example: RCC can handle 20 active units. When the 21 unit goes active all units would get a 1% penalty, almost unnoticeable. The 22nd would induce a 3% penalty to all units, 23rd another 5%, etc.
Another add on to this is being able to turn units off like you can buildings, which opens up some interesting game play opportunities I'll blab about in another post.