If it is block construction the engineers will make you beef up the slab and add piles to support the new weight of the second floor.

Just last month, from what I read in the Wall Street Journal, there’s been a growing interest in these more under-the-radar markets.. places like Casper that might not scream top-of-the-charts popularity, but quietly attract buyers who appreciate untapped potential.

After weighting all of that, does it make the most sense to try to keep this tenant in place? 

I find with ANY project on a property, PLANS are worth their weight in gold bc they will show the exact inches, ft, etc that the project entails.

If it turns out well a good lender is worth their weight in gold.

BUT for certain rural areas it's worth it's weight in gold because of the reliability factor vs an unreliable or expensive existing utility structure. 

yep your weight in gold.  

They may or may not have good reasons and unless they communicate those reasons and perhaps even substantiate them I really try not to give them any weight.

Contrary to popular belief, this is not set because I believe it will give me a higher return.

As others have said, fitting what is popular in your market or what will sell best is always the best strategy.