This is something that’s been driving me nuts with final cut as well.
Panasonic have announced a plugin which allows native AVCHD editing in fcp 7 to be released in the summer time (not sure about 6).
You can also re-wrap the files into a mov container which fcp is happy with ingesting natively – check ClipWrap (https://www.divergentmedia.com/clipwrap). Although editing performance is not so good.
This strengthens the question about whether Apple can even be bothered anymore, like if a re-wrap is all that’s needed to allow native avchd editing, not a ground up re-write of the software, then why the hell have they not addressed this with a patch?!…
I’m a fan of the ProRes workflow (i love I-frames) but it just seems unecessary, when you can chuck a card in, dump the clips in Premiere and get editing straight away, with multi core and cuda, you get stuff done in half the time, which is what really counts.
rant over