[TheGyrator]

This really has me really at odds.
Can I just create two mill profiles in Mach 3?
One configured for Imperial and the other for Metric?

That makes the most sense IMO.
I use so much of both it makes no sense to commit to one and honestly most anything larger than 3 at most 4 inches I will always use imperial.
When it comes to milling precision parts obviously metric will be preferred but at the same time when it comes to scaling common items or even not so common, a lot of stuff I've made by hand over the years was best produced by inches particularly when it needs to conform to frequent hand grip or touch or some other form of physical contact and interaction.

[keebler303]

Yes, you can do that. You just need to change your steps per unit and associated settings.

[TheGyrator]

I went ahead and took the 2 minutes to create 2 profiles and it works.
Metric Mill
Imperial Mill

I assumed the software would be intuitive in this way and it is but I'm a beginner so you never know the reasoning behind methods within industries that to the novice seem counter productive but will always prove to have very good reasoning behind them. I imagine if a shop used imperial and had different employees on the same machine setting it so all are defaulted to imperial units and motor settings that can't be changed would be typical.

Anyway for any other beginners wondering, it works just be very aware of your g-code files when you load them since some are metric and some are imperial.