Mid drive would definitely be favored if you will climb significant hills often.

Here is link to e-bike use on Boulder paths - you may wish to check with local venders etc too:

https://bouldercolorado.gov/goboulde...-policy-review

If this will be an on-going thing for you maybe a vendor you buy from in Boulder can help you out (store the bike?) and perhaps have battery in good condition when you arrive and bike ready to ride. Maybe you apply what you would have spent on storage toward their servicing.

Maybe they will just rent you a bike?

Here are a couple of places in Boulder that deal in e-bikes although I don't believe they handle BionX:

Small Planet EBikes

https://optibike.com/