I don't think that would do very well. I have had a custom custom before, and as a general rule I think they fair better as bridge pickups because of their higher output and the way they are EQed.
Might be a reason why they are not offered in neck models.
In all honesty though, I am sure at least 1 person on this forum has tried it, and probably made it work. The main hurdle would probably find a pickup that has enough output to match the one of a custom in the neck.
hamer makes/made a guitar that had a sh5 custom in the neck with a tb11 custom custom in the bridge. i thought it was a really sweet combo. very high output and hot sounding in all positions but still musical.
the ceramic magnet custom in the neck was great for solos. the best clean tones were with both pups active, with either one by itself the cleans werent that great but the dirty tones all around were really nice
back in the old days they didnt usually have ceramic pups with extra turns either. it wasnt really till aftermarket pups that you started to see hotter things start turning up. a 8k alncio 5 pup could be a great neck or bridge pup for lots of people. a 14k ceramic pup wont suit everyones tastes, especially in the neck
I have a Hamer Studio with a Custom in the neck and a Custom/Custom in the bridge (soon to be a Custom8). Sounds absolutely killer in all positions. The Custom sounds pretty good clean, a bit dark, but that can be dealt with using those knobs on the amp . Splits great and sounds absolutely killer under gain. The best shreddy neck pickup I've ever used. I would have expected it to be a muddy mess, but it's not at all. It also balances well tonally and output-wise with the CC in the bridge. Highly recommended by me!
I have a custom in the neck, wired in parallel.....love it for sparkly clean tones. IE: Far Behind~Candlebox, Enter Sandman intro.......I like it! It's very clear and cuts thru in a band situation. I plan on adding a series/parallel switch because it may sound great when clean in parallel, I want it in series for neck pickup soloing. I had a thread about it last month or so...........Here it is!