Tiffdruck and rotogravure are really fascinating processes, and the benefit of the copper plate was that it could be used to print thousands of copies without deteriorating.
So what would be the benefit of a polyester version?
You could essentially create the same type of printing plate with gelatin on PET and a screened negative. This could be used for bromoil/oil or dye-imbibition.
But, ok... maybe I see your line of thinking now. You want to transfer palladium toner (for instance), which is an aqueous solution that wouldn't necessarily function like an anionic dye (dye imbibition) or a greasy ink (bromoil/oil). So in this case, it seems like you're looking for the ability to transfer something other than an anionic dye, which has a unique relationship with gelatin, or a greasy ink, which is needed for oil printing wherein a water-saturated gelatin relief repels oil (a non-polar substance).
Now, as for etching polyester, I have no idea how to do that. Polyester film, a.k.a. PET or polyethylene-terapthalate is notoriously reistant to all kinds of nasty chemicals. So first you would have to find something that will eat away PET, and then you'll have to design an inkjet cartridge (probably out of gold!) that won't also be destroyed.
Forget about printers; the things you want to do are better achieved through analog means...