With SALT tracks I'm going to make a guess that they have alligator links for the master and that's the reason he wants to just cut a link so the alligator link will remain undisturbed. That said if a link is to be taken out then it will need to be done by a shop with the proper tools to do the job.
If you were to cut and try to weld a link, in an attempt to do the job on the cheap, all your doing is asking for trouble. What's going to happen is the first time the man gets that track in a bind the welded link is going to break apart at the weld and the track is going to fall off. I say this because track chains are made of a hardened, cast alloy and typically do not take weld all that great. Over the years about the only thing I've ever seen welded on a track chain is the alligator master link itself. Usually thye run a bead right down the joint to help hold it together when the bolts break. The way they are made all the weld is really doing is keeping the alligator teeth together so it's not taking the full pulling force applied to the track like a cut and welded link would be doing. Even so, I've seen just as many of the welds cracked and nearly broke as I have welds that have lasted any length of time.
I could say more on the subject but if I were asked to do this I wouldn't do it, and would strongly recommend that the customer not even attempt it because he'll wind up worst off than he already is when the welded link fails.
That said, the other posts saying that the track wear indicated that everything was worn out and removing a link still wasn't going to really solve the problem is also right. However, if it were a set of standard unsealed tracks, and the guy was just using the macine for occasional, personal use, then it could be done. Still all that would do is cause it to wear the rest of the remaining parts faster but with little to no use, it wouldn't be a real issue. The main issue here is that a welded link simply will not hold up.........