As I have said to me its a skill flavor thing.
Mechanical does not feel like using the force to attune a lightsaber.
It feel like its a skill most Jedi don't have so we are using it as a balance thing.
Wait it makes it to hard for Jedi to make a good lightsaber lets give them a -2p bonus.
whats the point just use Discipline a skill already linked to the force through force powers.
if mechanical does not pull you out of the game then fine use it, but for me and my group the suspension of disbelief drops on this one.
To me its like saying use your piloting skill to uses a force power as a balance because its something most force users don't have.
For the record this doesn't exactly dispute what Daeglan and others have said but basically confirms it.