i think there are two points being made here. one is that for some very low tech people (none of which are necessarily members of the forum!) it might be nice to have a tc demo that has a browser and flash already in the iso. (naturally to have flash in the iso almost certainly violates some copyright, and it's not the sort of thing i would offer for download, but i do like beafanatix, which is an iso that includes flash 9 or compatible.)
but the other point is that there are a lot of things you don't need to open up and remix to get them working. you could make an iso that has the extensions included, or you could use multisession...
however, to get permanent this and that, i believe roberts has already created modes that allow you to do what you want, and without a need to remix anything but to include extensions. it's simply a matter (i believe) of putting things in the right place to be found on boot? not of reconfiguring tc.
and as for flash, i suppose you can include getflash without violating anything at all. people will still need to run sound on from the oss menu, and getflash from the menu.