You can use a gasser to blow glass, and you can use a glassworker's glory hole to work steel, but neither is much suited to both tasks if it was built for just one purpose. I have a design in the works for a firebrick forge that would be triple-role (glory hole, forge, kiln) with several different doors for various functions... but in general, given the relatively low cost of building gassers, you want to build multiple furnaces suited to each role. Working glass offhand means you are working with stuff that is flopping around madly sometimes, will definitely do damage to your liner (replacement every 2 years) and needs a lot of space to move -- working steel in a gasser is usually the opposite of this, in that it doesn't need lots of space beyond having a fair bit for the burning gases to circulate in, it doesn't move around much, etc. Also, for glasswork, usually two or three "furnaces" are used: annealer, glory hole, and crucible furnace, or if you're Italian, a lehr (continuous annealer) and dual-role furnace. Annealers nowadays are almost all batch annealers and run on electricity -- if you can't run a 240V@15A line out to your shop for a day or two at a time, you're not going to have a lot of fun blowing glass. For more info on backyard glassblowing, check out Mike Firth's
"Hot GLASS Bits" website. Good luck, and feel free to email me (or preferably continue this board discussion) if you have any questions!