So I'm crafting up a PC concept for my players and one of them is interested in playing an Engineer (Saboteur). Yet we noticed that despite there being information that Mechanics and SKulduggery are most often used to make stuff go boom or wreck things via sabotage, there doesn't appear to be any gear associated with actually accomplishing this.

Any thoughts on this?

There is the Talent in HG/Demolitionist. I suppose you could come up with some limited form of that which is harder, or just roll a HG/Demolitionist.

While it might be a while before its covered in an age of rebellion supp, the EotE dangerous covenants supp includes several different kinds of base explosives and how they combine to make a big enough boom to blow just about anything to kingdom come.

Also there's a dedicated demo man spec if you really want to get nuts with the pyro.

Making things "go boom" should be able to be handled with a skill check and an appropriate Tool Kit. Skulduggery or Mechanics as appropriate. Additionally, certain tasks might take a Hard mechanics check but only an Average Skulduggery check, or vice versa.

Right now, the only thing in the AoR rulebook are anti-vehicle and anti-personnel mines. I think these could work as a starting point if all one has is the Age of Rebellion Core Rulebook. Otherwise, Dangerous Covenants is an excellent pick-up to flesh out explosives and how to use them. The rules are entirely transferrable. Both the Demolitionist (EotE) and the Saboteur specs were developed concurrently with each other, and frankly would be quite compatible.

The last EotE game we played, my Outlaw tech produced a detonite charge using his Utility Belt talent, and managed to fashion an explosive that was used to enhance negotiations.

For a particularly complex explosive device, I could see the Contraption talent working.