Yes, they should be able to roll on and roll off though IMO that ability is different than a light vehicle cubicle. I really wish we had something for small craft to be able to do that- a LCT type, similar to how armored vehicles are secured on lowboys, railcars and aircraft today.
For tactical deployment from Intruders or other combined arms transports I would absolutely imagine that the infantry load up in their APC/IFV/ISV, strap in and enjoy the trip planet side. The vehicle driver is instructed by the loadmaster what order their unloading would be, some DS crew personnel would play ground guide to the driver & VC/TC, down the ramp and out on the new planet.
But those troops are not sitting in the vehicle's troop space the whole week or so between the planet and jump point or however many weeks they spend recharging to jump to their destination. A (real) mechanized infantry company will need 3 platoon bays (15t) and either 3 light vehicle bays if you are using platoon-sized transports (150t) or 12 light vehicle bays if you are using squad-sized transports (600t) which is a waste of DS transport space.
Add to this not all infantry units will be mechanized or motorized- a vast majority should be regular foot, LPCs being their mode of transport. Others could be airborne, using either conventionals or small craft for their air drops, some will be engineers, some will be military police, and even more will be support troops. Techs, quartermaster/supply, admin, or any of the other 'tail' functions would use 'infantry' non-combat transport methods. Each will have their own vehicles to transport and they should not go in a vehicle cubicle- though I admit I have planned on occasion for mech repair equipment to go in a light veh bay for my mercs.
Next consideration would be the MASH/CASH team . . . I think a Fury would work well for a small medical support team transport though a Condor might be more appropriate for a RCT combat movement . . . though it violates the 'eggs in 1 basket' rule.
Staying outside of the RCT transports and some of the 'discovered' SL stuff like the Lee & Colossus . . . IMO the most JS-friendly way to move a RCT for a invasion is to use-
Combat Drop
8 Overlords
1 Fortress
1 Union
1 Excalibur
2 Triumph
2 Intruders
1 Condor- MASH
2nd Wave
2 Jumbo- Armor/Infantry/Techs as cargo w/supplies
2 Jumbo- Supplies
1 Aquaduct- fuel carrier
21 Dropships not including what is needed to get aero support to the fight, or gunships for escort. Mechs set down in 8 battalion transports, 1 company transport and part of 2 combined arms transports. The combined arms transports will deposit 2 armor regiments and a company. The armor transports puts another regiment into combat, and can have roughly a battalion of infantry in place. Honestly not sure the Triumphs are needed if a commander can get one of the rare Excaliburs.