Sulfuric acid will add sulfates to the water, so there is no free lunch here. Hydrochloric acid will increase chloride. Between the two, chloride is more innocuous as it takes fairly high levels before it becomes a problem. With sulfates, lower levels can increase stainless steel corrosion (when chlorides are also present). Besides, ALL sources of chlorine will result in increasing chloride levels in the pool so there is no avoiding it -- if this guy is that experienced, he should have known that. For every 10 ppm FC from ANY source of chlorine, it will result in 8.2 ppm salt when the chlorine is consumed/used. With chlorinating liquid, bleach, or lithium hypochlorite, there is an additional 8.2 ppm salt so a total of 16.5 ppm salt (sodium chloride though if using lithium hypochlorite it's really lithium chloride that is the result). See section VI in this EPA file
that says the following:
Non-halide salts have little effect on stainless steels, but chlorides particularly tend to promote pitting, crevice corrosion, and stress-corrosion cracking. In some cases sulfates seem to aggravate the effects of chlorides. Chlorides present in amounts as little of 0.3% with sulfates present can produce severe corrosion. Even quite low concentrations of chlorides can cause corrosion when concentrated by occlusion in surface films. Oxidizing chlorides such as ferric or cupric chloride are specific for severe pitting, although halide salts can cause severe pitting and stress corrosion cracking. The austenitic stainless steels are, however, the most susceptible of all the stainless steels to “chloride” stress corrosion cracking.
As for fumes, one can just use half-strength Muriatic Acid (15-16% Hydrochloric Acid) which fumes a lot less.