Ah, yes I see your point where power could be a handful in 1st. There are two other options that might help without cluttering or weighing down the bike:
1) Make the mixture initially rich for 1st gear as that will further reduce the power and then lean in out in each subsequent gear (just be careful not to foul out the plugs). I did this with my scooter to reduce a 5hp hit to about a 2-3 hp hit to keep the front end down (fixed hit at the time).
2) Use a REVO setup as that allows power from 0%-100% and any percentage in between. However, this also requires the use of a controller capable of handling the revo. Either a Max Extreme REVO OR a controller (perhaps your ECU with REVO interface?) that can give the same outputs and that is beyond the scope of my experience so I'd get in contact with WoN in that regard.
Hopefully, this gives you some ideas that may help you to get the bike to your goals.