Why would each BA unit have to have it's own transport? Couldn't they be deployed in two waves? I don't view infantry and most BA as a hard-charging offensive unit, but as a defensive unit. In that sense, having two waves to move them from dropship to battlefield isn't a big deal if they're not getting tossed into combat immediately.
Ahh, I DO think of BA as an offensive unit, especially in the context of an LCT, so we probably have different expectations there. I also concede that you are probably correct that some portion of that force is expected to be defensive and doesn't really need dedicated transport. In my mind, that isn't more than 25% though. The transport-in-waves idea has some merit as well. I'm not sure what percentage is reasonable to be available in a single wave, but I can live with the idea that a couple units all share the same transport, at least in terms of VTOL transport. As I said, I thought of the VTOL transport as being limited and included in the headline numbers of combat vehicles. It's really the boring, simple, not-really-armed APC's that I assume to exist outside the normal ToE, and I probably assume a lot more of those than you would.
A lot of that comes from the idea that, while they don't have to lead the charge, BA infantry should at least be able to keep up with the rest of the force. That is absolutely a headcanon thing for me, not anything official. However, as battle is a highly mobile endeavor with mechs and combat vehicles, it just makes sense to me that BA should be able to keep up with the rest of the force when on the move. With little or no mechanized transport and limited VTOL transport, you just can't keep much of your BA in the fight if you are on the offensive. I think of it sort of like a Naval fleet: It is only as fast as the slowest ship. Without transport, your BA becomes the limiting factor in how fast the whole force can move, or your have to leave some potentially large percentage behind when you are on the offense. If you don't then your VTOL assets are split between re-deploying troops already on the field, and heading out to pick up another wave. If mechanized transport is assumed, they can hop back in the APC's when the battle moves and keep up with the rest of the battle line. Still, this is just my personal preference, and how I would envision things. No one else has to do it the same way!
Also, if mag-clamp BA was more prevalent, it would make this whole situation much easier to deal with. Who needs an APC when you can stick yourself to any old combat vehicle!