I had this idea running around me when testing Morph-tool that it would be nice to have menu like one on Psi gun exist on morph tool. With all wrenches you placed in it arranged in circle so you can choose one.

This would allow you to switch to wrenches even without items from selected mod present.

I know you don't want to add a key-binding for one item (And wholeheartedly agree with you on that).

I was thinking that Shift-left click could bring menu up while in vanilla mode?
Then after selection it would go to that one wrench and say something like [Forced] in name.
And to exit from forced mode you could press drop but instead of dropping it would revert to auto-choose mode.
If you shift-drop when in force mode it would still unbind selected wrench like normal. (This would also allow player to be able to drop a wrench even without any blocks from its mod present)

Sorry i know its similar to #2 but it seems like good mechanic for me.

Thanks for reading.