I found some templates in an old white dwarf and modified them for my needs. I'm not going to distribute them here, but I'm sure a quick google would find them. However the original tank they did in WD was somewhat, erm, dumpy. So I stretched it out a little bit to be more inline with the modern superheavies.
The premise for the modularity is quite simple. I'm going to do two track units, then link them together with two tubes. Then the centre unit will be changeable. This means, aside from the storm hammer, all existing variants will be easily possible, along with the new ones I'm going to create. The Storm Hammer only causes a problem because it has extra sponsons on each side. I'm toying with the idea of working this into the design, but who knows, by the time I've done the Shadowsword, Baneblade, Stormblade, and Stormsword I might be bored of stcs..