That being said I will be using my FT heavy crusers as the biggest heavy crusers with attack criusrs as smaller heavy cruisers. Light crusers will be represented by light cruisers and heavy destroyers. destroyers will be represented by destroyers and smaller classes for the small destroyers. Battle crusers and battleships will keep thier designation. I have no dreadnaughts but if I get some, the battleships will slip down to represent big battlecruisers
Good plan! If you look at the Appendix I construction table, you will see some fairly obvious division lines.
DD's are all size 1, but have max armour split between 2 and 3 (tonnage 40-58 and 63 to 84 respectively).
CL's are all size 2, but have max armour split between 3 and 4 (tonnage 90-116 and 123-152 respectively).
So both of these classes already have some guidance as to how to differentiate tonnage wise between the larger and smaller in the same group.
CA's are where it starts getting really interesting. There are a total of 2 hull sizes (2 and 3) as well as 3 maximum armours (4-6). This gives 4 ranges:
160-194 (size 2 max arm 4)
203-240 (size 2 max arm 5)
250-292 (size 3 max arm 5)
303-348 (size 3 max arm 6)
The same trend follows on for BC's and BB's (4 ranges each). So really, the game easily handles 16 different sizes of ships - with minor variations in tonnage within one of those for different fit outs.
I was thinking for GZG models that the ones on the larger metal stands would be the Size 5 ships. Heavy BB could be a size class 4 BB, and the regular BB could be a size class 4 BC and so on...