Then you are now getting your coil power from the main battery rail, just as your glow plugs themselves do.
I don't see anything wrong with that.
Just means your control wire is now active regardless of your key position.
The way it was wired, the key had to be on in order to power the coil that engaged the glow plug power.
By powering the coil directly as you have, you no longer can kill coil power by turning off the key. Your control wire gets shorted to ground anywhere or your button hangs, you can no longer shut down with your key.
Anyway, that's the only caveat I see.