A quick edit to my reply on the mini scale turned into, yeah, enough for another post, lol.
Copied from my edited post, and added to.
This is actually the second Rhino version. The first was even smaller. When this model was made, the scale of the figures was still 28mm, and the model was now scaled properly, however was still too small to fit 10 Marines inside. Kind of like the Aliens Colonial Marines APC. We know exactly how big it is. And we also know the like the TARDIS, it's bigger on the inside. GW started to increase the size of the Space Marine minis, an now the model is once again underscale compared to the minis. The Primaris Marines that come with the box set are 38mm, and I think the current Firstborn(real Mk7 Marines) are somewhere around what you said.
I like the older 28mm era, so using the width of gets this. Which would work, barely. Especially if you take the lore into account, and remember, in the end, this is 40K, the setting where punching a tank with an oversized armored gauntlet is a viable and often effective tactic. It doesn't have to make sense.
And, as I need to keep reminding myself, in 40K, vehicles are massive. The Rhino, an APC, is bigger than an M1A2 Abrams. I don't have a 1/18 M1 anymore, so here's a 1/16 one instead. It's already wider than the 1/16 Abrams. And it still needs to get bigger.
The Rhino is an ancient Dark Age of Technology STC product. Therefore, they were around before the Space Marines were created, and was designed for normal humans. It is also currently used by the Adeptus Arbites and the Sisters of Battle, normal humans. It was once a pretty ubiquitous Imperial vehicle, but sincw the Horus Heresy they have become so rare and precious now they're restricted to those three. So it should be cramped for a full 10 man squad of Marines, but do-able. I see it as a capabilty that is used during major battles and emergencies and the like, with most of the routine use being by 5 man combat squads. The squad leader in the TC position on the left, leaving 4 Marines in the troop compartment. But there still needs to be space for 9 Marines to physically fit.
But I also need to make sure that a Marine can use the side hatch, and use the cupola hatches, and this is still too small, but verrry close. Now comes the artistic license part. Like the gamers who convert their Rhinos to "true scale", I have to enlarge it to fit the Marines. But unlike gamers, I also have to make sure that the design will actually work. So the road wheels and track need room to move, the inner hatches need to slide, and that the rear ramp can be remotely raised and lowered.
