The suggestion is to have the new signet skills compliment the mech theme but give a little more control back to the player by making the active effects similar to conjured weapons for the engineer based off of mech parts or weapons.
That's the main idea and there is plenty of room for adjustments, balance, etc.
Imo I felt that as the mechanist the player lost a lot of control to do the dps, support, etc reliably or was not as responsive. So I thought that the new skills should augment the engineer to provide mech themed gadgets, weapons, utility, etc.
This is all just thoughts and opinions though.
