I'm neither a wide body nor wide serrations nor square trigger guard nor FCS guy.... But that's a cool looking gun. You going to do a thread on it when it's ready?
[and yes, bill, I like yours better]
I had a LWC that wore np3 really well. My next refinish -- an izzy highpower -- will probably be my chance to try NP3+.
I'd recommend against the FCN. Especially if you are going NP3 afterward, if you can get the plater to even do it. I would expect adhesion issues to surface in attempting that.
I'd leave it as bead blasted stainless.
FCN is at its best in a wear resistance application, like a gear. Not an impact loaded application, like a gun. Glock gets away with it because their steel is a nice buttery soft alloy.
How can you tell it's custom with no serrations on the arse end of the slide? Duh. ;)
(I can't remember which custom make it was... maybe Les Baer? ...who said that the main reason his guns have FLGRs was because people expect an FLGR on a custom gun.)
That being said, if there was any place where reflections on the rear face of the slide might be annoying, it'd be on a dot-sighted pistol with a stainless slide, so there's that...