Exactly that I have done some time ago in my branch - start re-layouting from frame where you change samething. Additionally I check if last character in edited frame change during edit - if not next page was not touched and re-layouting stop. In my sample document with 160 linked frames A4 and text with 9 pt (if I remember about 200 000 characters) simply editing was as fast as for one frame. Worse was when you change style and you are on the last frame.
BTW I am not sure if very big precision (double values are used in Scribus) are required here. I even try to switch values and calculations to integer type (where 100 is one real point, so precision is 0,01 point), but I give up (very massio refactorisation of code) cezaryece
