Hi, yes with the right tips you could certainly do both of those, and a rosebud tip is also an excelent source of localized heat for blacksmithing.
However, I'm pretty sure you would need to manifold several tanks together to do either one on material that thick.
With oxy-fuel, you can weld,braze,cut,solder,apply localized heat. The learning curve is not to bad, Probably easier than learning to run a stick welder well. But harder than running a mig. If you can tig weld already then it won't take you ten minuits to get it.
As far as cost,the torch ,hoses and regulators are only part of the cost. You must also either lease, rent, or buy a set of tanks. Also you must pay to keep them filled in most cases. Which could get quite expensive if this is the only welding setup you have and you use it a lot.
Personally I have four torches and three sets of tanks and wouldn't be without them. But I also wouldn't be without a good stick welder also.
Around here you can pick up a decent used 250 Amp AC/AD welder for under a hundred and fifty bucks.