1. Is there a restriction in either the driver or the physical hardware that would prevent me from manually cutting and feeding a 17x40” sheet through the printer successfully?
Pre-cut sheets should work , it's just a matter of finding out what lengths the printer can handle. Early word is that there's a 38" limit, but I think the definitive answer will have to wait until it starts shipping (or at least review samples start shipping). It could be that the the 38" length is what's officially supported, but the print driver may accomodate longer lengths if you're using a custom page size.
2. Is there a restriction in the hardware or driver that would prevent me from creating a paper holder for the roll (glorified TP holder ) and feeding the uncut paper through the printer, completing the print and manually trimming the print from the roll?
I doubt this will work, because a printer has to handle paper feeding differently when using roll-paper. It has to know not to try to feed the paper completely through or it will end up feeding the entire roll onto your floor.
If it is possible to use roll paper in this way, then it would be essentially the same as the way the 2400 works (no built-in cutter, but the driver can handle rolls). But I have a feeling Epson isn't going to allow this functionality because they still want people to buy the more expensive 4800.