As i'm presently doing option B ref: restoration due to chassis - - restoration = forget your timeline

forget your original plan and budget
and almost forget about picking up a plug n play replacement chassis, crashed ones might be bent, and any that have come from otherwise scrappers are probably also in need of rust prevention - maybe not as bad as yours but as far as work is concerned, you'll spend as much time on it
By the time you remove the tub off the chassis ( not such a big job in reality), you would be daft to "just" do the chassis - i'll not detail everything - but it is just about everything else you'll end up doing
brakes
bushings
ball joints
secondary chassis part restoration and suspension part restoration
engine - auxiliary part's replace or repair, main service items
wiring loom inspection and repair
oil pipes, water pipes, power steering pipes
and any otherwise hidden repairs needed
and the removal / replacement of stubborn nuts bolts self tapers etc..
Then! you can have fun with tuning, cosmetics, interior, tub outrigger restoration etc...
The answer is in the book "Zen and the art of motorcycle maintenance" - is it the use of the end product your after, or is it the journey to getting there ? - if its the later - enjoy the journey the value to you will be priceless
if its the former, get the cheque book out and buy a decent one - enjoy the drive