I have used helicoils in oil feeds before to quite good effect-its not somethign that you constantly do/undo and they aren't under any real torque or load. So the drain should be fine.
If it fails when removing a bolt, just whack a new insert in (or I've put a tiny bit of jb weld on the outside of the insert instead of loctite to make it more permanent).
Timeserts are more permanent helicoil - but got to watch how much meat there is to go wider... its not huge on the drain.
The bigger banjo - potentially it may drain too much??? and you have to get a different drain etc... plus there;s not much meat to go wider.