I haven't used it, but I like the aesthetics of the FC660 layouts, which is why I've got a clueboard on order.
However, I'm planning on making my fn the 1u in the bottom row (instead of the winkey) and doing a split right shift to avoid having to get 2 left shifts for future keysets (which I think is the biggest drawback of the original layout). My only issue is currently not knowing what the heck to use that extra 1u from the split shift for.
Functionless TKL is interesting, but might have awkward proportions in practice? And having it be programmable makes the home/end/pgup/pgdn keys seem a little redundant to me. Could still be cool though.
The 65+5% is cool though, in all honesty. I could see that short shift being a point of frustration, but your board looks nice.