Gone...
The issues on your mind probably force versatility into a top slot on your list of priorities, and I believe oxyacetylene might be a good choice. Certainly it bears serious consideration..
It's an indespensible tool for all kinds of repair work and I wouldn't be without one. Its also my personal opinion that familiarity, if not proficiency, in this process will make all other welding processes easier to master, and other issues, such as outstanding portability, less cumbersome protective gear, and other advantages make it my first choice. It welds, brazes, solders, cuts, bends & forges, loostens frozen nuts, slices, dices, and does everything except fold up your socks and put them away in a drawer... I exagerate only slightly... it's a pocket blacksmith shop in trained hands, not merely a welding device, and pardon the pun, is the hot ticket for the farm.
The advantages of "stick machines" as well as oxyacetylene become clear when you have to buy unnecessarily large, expensive reels of wire for some obscure small repair you might see once or twice in your MIG welding "carreer", and upon investigation you'll find there are products suitable for oxfuel use available which will enable you to complete all those projects in steel, aluminum, bronze and brass, copper, and stainless that you are thinking about.
Oxyacetylene simply does not come to mind when we think of welding equipment, but I would place it first ahead of stick, tig, and mig in that order of personal preference for your purposes. As you are still orienting yourself, a good place to begin would prhaps be to explore why they're in that order when you talk to pops friend.
(I could, and often do, go on and on, but I'm out of time for now but will follow up if necessary)
Good luck and regards,
d