If I am understanding you, you want to 'splice' the signal wire of the neck pickup into the signal wire of the bridge pickup, correct? If so, yes, you could do that.. But, personally, I would just extend the neck wire by splicing a wire onto that by itself, keeping it separate from the bridge until it reaches the jack. It will just make things easier down the line.
With that said, if the problem is that BOTH the bridge AND the neck signal wires aren't long enough to reach the jack, then splicing both to an extension wire ('Y' junction) would be what I would do, just use a good extension wire (stranded, 26-22 awg). Or you could use something like
Wago 'Lever-nuts', I have used them in the past on other wiring jobs and they do a great job securing smaller diameter wires (though they are a little bulky themselves)..