The problem I see with following 5.0 with 5.1 is that, except for some diehard bitheads, normal people would assume "1" means the first, and this is the second... so I get the logic of "5.2"
A challenge with reflecting the fifth-wheel design in the model designation as "5.0" is that the 5 is likely to be assumed to be a version, which it's not. As soon as people think that way, any convention gets in trouble... I would want to lose the dot, even if it was
an amusing spin on "web 2.0
The rest of the Escape models are named just by length... and in feet at that, which makes sense in the U.S., and quite not as much sense here. The fifth-wheel and conventional lines thus have inconsistent approaches. Maybe a solution is to put the length back in, but keep the "5" in some way. "5/20" (for a 20-foot fifth-wheel), or "5/615" (for a 6.15 metre fifth-wheel) to start a new metric convention as used in Europe (and on the old Trillium 4500 and 5500), for instance.
"TA" could be tacked on the end, but the other models don't currently do that... its a "19 Foot", not a "19TA". Model names can easily get overly complicated.
If you use nothing but TA to distinguish the new one from other fifth-wheels - so the new one is "5TA" - what do you do for the next
fifth-wheel, whether it is a replacement or an additional size? It would also be a "5" and "TA".
I guess I would suggest something like "5/615", but I only know what makes sense to me, not what makes sense to or attracts others.