The type of shield that fits on the head is the only way to go for all kinds of welding .
It leaves you with a free hand to balance yourself , manipulate the rod or scratch your arse .
The electronic dimming helmets are getting cheaper every day and make tig welding very much easier .
It just occured to me that if you have a reasonable quality DC stick machine that you would not need a specialised tig machine as long as you confined yourself to tig welding steel because a machine of this type will let you do "scratch start" tig .
I would not bother with the cheap mig machines ,they are nothing but trouble and the weld quality is terrible .Mig can give a false sense of security in so much as it enables you to produce a passable looking weld but the weld lacks penetration and strength .But if you plan on doing a lot of thin guage ,a better quality machine may be an option and can produce good welds with the right shielding gas.

Yes, the cheap welders are not so easy to produce good work, I bought a cheap welder back in the late 70's to make fittings for a boat I was building. That welder paid for itself in the first week. However i often wish now that I had bought an oil filled Oxford as having to wait for my little machine to cool can be a bit frustrating. I have bought a new fan cooled one here in France as my old uk machine did not like french electrics... I am way ahead of you re the lack of penetration on cheap migs, is why for farm work I prefer the stick welder.
This whole project sort of escalated. I needed to do some fine work, and thought tig was the way to go. From there it escalated into making up a set of panniers from aluminium. I think I could never justify buying aluminium welding capability now I know its' requirements. Probably resort to using steel screws and araldite :)

Why don't you mock up a set of panniers in cardboard and then cut and bend aluminium pieces to match and get a good local welder to tig weld it together for you .
The frame you can fabricate yourself - out of steel .
That way you have a set of panniers that are custom designed to your requirements and all the time consuming preparation has been done by yourself ,hence making the job a lot cheaper .
I made myself a set of panniers last year ,"borrowing" ideas from Jesse, Tesch and Happy Trails .I think it is important to "round off" or 45 degree the corners where the panniers might contact your leg in a fall , there have been a few broken legs caused by hard panniers .

Thats a good point, never thought of that...