My wrist is around the same size, possibly a smidge bigger and quite flat also. I have the 43.5mm, the lugs sit nicely between the edges of my wrist so definitely not stupidly sized in that regard. However I agree with your statement, it is just too big and heavy for a daily wearer.
I think the biggest I'd probably want to go for as a daily would be the current seamaster pro 42mm, which I tried on last year. I'm toying with the idea of flipping my PO and getting the new white dial SMP. However, I do love the quick hour set you get on the 8900 movement in the 43.5mm PO.
I'm worried I'll miss the PO if flip it. I just don't know if I want another omega in my collection, as I've already got the PO and a 2500 SMP, which I got for a very good price so don't really care that much about and use it for work etc.