I like the idea of a hand amptrol unit, but I haven't found one that I am particularly happy with. These seem to come in two versions: one with a side wheel and one with a linear "slidey thing" (i.e.something like a belt that runs on rollers that slide up and down the unit). I have the "slidey" thing version from Lincoln, and I am not crazy about it. Unfortunately, I hear the same thing from the guys who use the wheels.
If you can, find a welding supply store where you can walk in and try the different styles, with gloves on and everything. These things are not cheap, and you may as well get one that works the best for you. (For instance, the wheel-based Miller hand amptrols come in an "east/west" version as well as a north/south version.)
Here's some more food for thought: for mild steel, I only need an "on/off" function for my torch once I get my machine set correctly. In my experience, that is much, much easier than trying to maintain a proper amperage with a gloved finger on a movable switch. You should be able to compensate for any small variances by managing the way you feed in your filler metal and the way you maintain your arc length, especially if you have any experience stick welding.