If you to get a crude idea of the control needed with TIG grab yourself something like an M8 washer, pen and a sheet of paper. Using the pen in the centre hole of the washer move it along the paper without drawing on the paper or slipping out of the washer. That's kinda the control needed with regards to arc length... OK maybe a tad harder but then the paper isn't hot and you don't have a weldpool or filler wire to worry about.
Obviously with something like a rollcage you need to able to weld while groveling around on the floor/welding overhead etc. As Langy said the tubing alone won't be cheap and then there's the kit needed to bend it cleanly...
Obviously with something like a rollcage you need to able to weld while groveling around on the floor/welding overhead etc. As Langy said the tubing alone won't be cheap and then there's the kit needed to bend it cleanly...




I will look into chroming steel cds instead! 
He was an engineer/ fabricator, the only thing he hasnt got is a working welder.