I use vec_for_vertex a lot and never had a any problems with it on speed... I don't think I've ever hammered it as hard as you plan to... I think your best bet is to simply give it a shot.

If worse comes to worse, you can always do it the old fashoned way and create each model in the correct relative position to the base model, like we did before we had vec_for_vertex.

Each base model would create all of it's sub-parts and each of them would position themselves with vec_set(my.pos,your.pos); my.frame = your.frame.

Good luck... let me know how you make out.

- WildCat