I don't see what is added by making battledress into a vehicle rather than armor. Armor rules aren't necessarily consistent; the rulebook describes the armor, everyone nods heads sagely. This is how it would look (I think):
Medium TL 13 Battledress - powered armor, AC 24 (+10 armor, +5 agility, -1 size), AR 10. Batteries operate 2 weeks without recharge (first departure from vehicle rules - all other personal equipment runs on batteries). A person in battledress will have an effective str of 20 and an effective Dex of 10. Battledress helmets contain medium range communicators, infrared (1km), and light intensification (1 km). Maximum speed in battledress is 10 kph.
If a marine in battledress can only fire and move once every five rounds, the Imperium isn't paying any 95 KCr for battledress, I guarantee you, if a guy in combat armor has only 3 armor rating less and moves and fires five times as fast.
It appears battledress moves only every 5 rounds but can fire each round (when using personal weapons), as per personal attacks in vehicle combat (p. 159).
It looks to me like battledress has a move of about 16m (11 squares), moves and fires normally, and has AC23, AR10. That's a LOT simpler than trying to make it into a vehicle, and it keeps to the spirit of the original concept taken from Starship Troopers, etc.
Add by edit: The only question, if you use the above paragraph to translate vehicle into armor, is whether there is an additional 5 die reduction in damage which is supposed to be included. Note: if there is no agility bonus (which isn't a part of armor), and the ac is increased to 24 again by adding 5 to the AR, then there is that additional 5 dice of damage reduction cropping up out of nowhere. So PERHAPS battle dress is AC23, AR 15.
