Add new vehicules and others graphics - newbie questions

[NCarlson]

Would it be possible to move in the direction of not having id's at all, thus giving us a theoretically unlimited number of vehicles?

[WWTBAM]

maybe but then that would probably break all the ttdp grfs which isnt what we want.

[DaleStan]

Then there's the minor detail of the fact that vehicles can, and do, rely on their numeric ID for certain behaviours (the AI-control callbacks especially). If the ID changes, then the dependent behaviours also change. This will, at best, cause the grf file to do nothing, and, at worst, break whatever AI (new, old, or otherwise) that tries to use the AI-control callbacks.

A similar issue arrives when asking a train engine if the wagon you just attempted to attach is allowed to be attached. If the ID of the wagon isn't what the train expects it to be, then the train's answer is unlikely to be correct.