I have some old, patched quilts from my gran and the patches are NOT subtle - she'd just use the kid's boyscout badges or any other "patch" laying around. To me, those patches are super-cool and just another layer in the quilt's story, I'm glad she didn't hide the patches.
I'd be tempted, in this case, to use this spot for a quilt label. Put down what you know about the quilt's history, then add who it was patched by and when, and list who is now using/owning the quilt.
I doubt any future generation would feel this ruined the quilt.
OR, if you really want to keep the front as original as possible, put a label on the back to replace whatever you borrow for the front.
Either way, the patching is only going to make the quilt more interesting and beloved, at least it would for ME!