I think it would be better to put them back there, even if they are somewhat like the Mk:s, especially since we have the earlier P and P2 models that won´t fit in the Mk system.

As for the name order I think it would be better if the Mk field was sorted beneath the make and model field if possible. Maybe even the chassisfield could be sorted there. To keep the official name clean from workshop designations and selfmade numbers.
Like this:
1964 Opel Rekord L
[A]
1968 Mercedes-Benz 200
[W115]
1975 Ford Capri II
Mk2
1975 Volkswagen Golf L
[Typ 17] 1

Some models have the Mk in the name, and in those cases it shold be in the modelfield or extra info, since it´s the official designation.
Like the Triumph 2000 Mk2, but the 2000 Mk1 isn´t badged that way and I think it ws dropped again on the later 2000 TC model. It was still a Mk2 though, of course, even if the label came off.

The european Fords are also problematic since they are produced in both britain and germany. It´s ok for the british cars to have a Mk number, but for other markets it feels more strange since they are rarely (I think) referred to in that way outside the UK. Maybe it´s better to use a simple number like the VW for them?