Replacing 1" pipe

Fizz

with 2'. The pipe in question is a run-out from main, with 2 laterals and riser at the end.  How complex is it to replace the pipe and laterals which are 3/4"?  The piping is part of a Richardson, and is at least 80-90 yrs old.  Attachment 3 is beginning of run-out from main, attachment 2 is end of run-out to 2nd floor riser, attachment 1 shows lateral to 2 rads in forefront, and 2nd lataeral to 2nd floor rad(20sf of edr) in background to right; 4th attachment shows 2nd lateral above another run-out from main; and bottom add-on to kitchen with separate dry return and vent.  The kitchen add-on is not part of original Richardson system, has traditional traps in 2 rads.   The reason for re-piping is too many laterals and too much radiaton to run-out attached to run-out, affecting heat quality of rads.  If replacing pipe is too radical, would repiping lateral in attachment 4 to middle 11/2" pipe which is a run-out with single rad attached(50sf of edr) be better option?.  Also, repiping 2nd fl rad(24sf) at end of run-out in quest to kitchen add-on which is 11/2" pipe with 2 rads total edr of 118.