If a character has, say, Fabrication, Repair and Armorer, does he have to buy 3 toolsets for them or just one, which would cover all those fields?
Three tool sets.
Or, alternatively, as explained 386, he could Burn up a set of tools that counts for all three.
I believe such a set of tools would cost 13 points. (I assumed both Fabrication and Armeror would count as manufacture skills, and thus have a cost of 8).
Of course, even in a High Index world, that would cost three RPs at character creation. Ew.
I could see an argument for saying a workshop counted as tools for certain tasks belonging to other skills (Repair workshop -> Armorer tools) on a case by case basis due to equipment overlap (and limited by the fact you can’t carry it around with you).
As for the costs on things, I’d say Armorer is less than that. Fabrication is serious business but Armorer isn’t as high up in terms of difficulty and startup cost as building a tank or spacecraft. Definitely less complex than cryonics hardware. I’d peg it at 4 or maybe 5 at the outside. Still nuts but less nuts 
Thats true. You could also give it limitations, such as being a workshop rather than simple tools (the limitation being: It cant move!), which might make it more manigable.