Imperial Army

@AnotherDilbert I appreciate the Auld Skool High Guard stuff, Mongoose's rendition of the 5FW is written with their High Guard rules.
And something else I want to caution everyone about is that MWM has said over and over again that GDW wargames do not depict the units deployed or the results of the war in the OTU.
Just putting that out there as a reminder.
Indeed he has been quoted saying the board games don’t predict the course of the war in canon. I’m not sure I’ve seen him talking about the units involved, but even assuming he has, presumably he isn’t decanonising the Spinward Marches Campaign adventure he wrote. It just happens that all the units he mentions on page 9 to 16 of that work are exactly the same as units in the counter mix of the board game. This could all be an incredible coincidence of course.
One word - logistics.

The main reason I suggest a battle rider sized assault lander is that it can be equipped to provide the logistics tail needed by the troops on the ground.
Food, ammo, medical treatment, a safe area for rest and recuperation.

You could split all those roles up between many 200t craft, but the purpose of these ships is to put Imperial Army divisions in combat ready positions as whole units.