I remember reading in a 1911 book that 1 reason Glock would not get the contract was that they would not allow their design to be licensed to other mfgr. to allow ramp up during a war. During WWII there were lots of contract mfgrs singer sewing machine, etc. for 1911s. Is this not an issue anymore? I would think that most poly pistols would be hard to contract out.
Nowadays, nearly all manufacturers offer some type of polymer framed pistol so no, I don't believe it would be any more of an issue than with traditional steel and wood. there would be exactly the same problems with start up, proving out the molds, dies, and tooling, but only the material would actually be different.
Some time , if you get the chance, read up on the bear of a time Rock Island had tooling up for Springfields -03 during WWI.