I do appreciate that .... I have a rustyhope kit sitting on the shelf I bought for another project ..... I know exactly what I have with it if I use it. Current project brakes are good.
I have asked about this in the past, you are the first that answered that question about scarebird brake parts replacement.
Personally I think a original MC if in good shape and usable will be just fine.
I believe the braking system on your car is a engineered system? Works fine as is.
Now if you have original brakes, & modify the master cylinder .... you have to learn a whole new skill just specific to your brake system ..... I mean applying the correct proportioning valve size to work with your existing brakes. Simply not a one size fits all ... Will take test & tune to make all work correct.
IMHO I would update all the brake system & not just a part of it ????
Honestly I'm a big believer in fix what you have, then modify & grow with what you need.