The short answer:the original feats are balanced as a whole, not piecemeal.
There is a bell curve at work - many components probably would be interchangeable, and there is an effort to try and keep most affects being introduced near the center of the curve, but yes, the final checks are made by looking at the feats, and the feat chain
as a whole.
In fact splitting up componentes can greatly devalue them - the fencing chain is balanced around some evil synergy between it's parts. Same with flails. Some chains re balanced by active antagonism between the parts - benefit A works against
benefit B. A swap that removes that hard choice makes the componets free to run wild.
I had enough doubt to ask. Yes, I suspected I was cherry-picking, but then any request to deviate from RAW may be cherry-picking.
. I suspect if you were to fuse elements from two chains, and to be mindful of mixing the sweet with the salt, you could probably hit some combos that don't make most GMs blink when you ask if you could use it