Not a bad look! And yes, I'd presume that Marines would automatically have autorifles or laser rifles/carbines.
One thing about air/rafts: Books 1-3 ALSO have the G-Carrier, which is a specifically pseudo-military craft with weapons on it. If disarmed, it'd make a good grav-truck.
I guess it depends on which version of Books 1-3 constitute "Proto-Traveller".
I'm pretty sure that the 1977 printing did not have G-Carriers (nor speeders, which look very much like the snowspeeders in "The Empire Strikes Back"). Also, in the 1977 printing air-rafts cost $6 MCR, which made them very expensive toys.
By the 1981 printing, the Third Imperium was established and the G-Carrier and Speeder were added. The Air-Raft was reduced in price to Cr600,000.
So I think that you *could* make a case for very limited grav vehicles in Proto-Traveller. Use the 1977 air-raft. At MCr6, it is way too expensive to replace normal ground vehicles. It would be economical enough to replace helicopters and other VTOL aircraft. But it would not replace tracked, wheeled or ground effect vehicles. Nor would it replace high performance jet aircraft.
Heavy grav armored fighting vehicles would be technically possible, but absurdly expensive. If we assume that an air-raft weighs about as much as a smallish car -- say 1 metric ton -- and that costs roughly increase 50% per additional metric ton (i.e., a 3 ton air raft costs 2x Mcr6), then even a medium sized grav tank (say 40 metric tons) would be outrageously expensive -- MCr 117 each. No one could afford many of these (and they would be very non-cost effective).
Depending on materials and engineering tech assumptions, helicopters and tilt-rotor craft might still survive as less costly alternatives to air-rafts. EDIT -- Looks like a UH-60 transport helicopter cost about $5-6m in the mid 1970s. Assuming that (roughly) 1 Cr = $1 US in 1977, then the MCr 6 air-raft is an expensive alternative. It can only carry 4, while the UH-60 can carry 18 (including crew). If my cost estimates are reasonable (i.e., MCr 1.0 per additional passenger) then then grav version of the UH-60 would cost about MCr 20. This is ~4 times the cost of the helicopter, but it would be far more capable. So I could definitely see helicopters continuing as low-cost alternatives to grav vehicles.