I recently put RR in my Hofner Verythin, sounds just great - clear yet quite punchy and not thin, great jangly clean, great bluesy crunch and can do some very serious hard-rock tones too -, but you may find the bridge a bit too vintagey / low output if you like the JB (not that it's shy in any way, this little beast does deliver the goods when it's time to rock, no problem).
FWIW, my SG had an (old - early 80s) JB when I bought it (third hand...), I briefly tried a RR bridge on it and it didn't quite work for me in this guitar (nothing wrong, just not what I wanted for this guitar), replaced it with a ABomb and it just rules - but I'm not sure I'd try something that hot on a semi.
So well... The RR neck works wonder on my verythin and I think it should be as good on most semi-hollows, can't compare with the Seth Lover (never tried it) but if you want a fatter/smoother tone you could go for a Mule neck. Or perhaps an Abraxas set - never tried it neither but it's usually described as a kind of a more powerful Mule, should be low-output enough to fit a semi yet with enough balls to please you.
My 0.2 cents...
