DSCR loans require upfront work to calcuate multiple factors based on either the PITI or the ITI and know your ratios up front. 

I have already lined up a professional property manager (the STR is out-of-state) and a design team (we are upgrading every room in the house and adding a ton of amenities). 

At that point, an appraiser would check to see if it operating as designed.

You didn't cause the problem which is a major factor in the premium impact.

For you, is having a 5-star overall rating on rental sites the most crucial factor for success, or are there other aspects that you consider even more important?

Here are some factors to be considered.Interconnection - This is a very deep topic and biggest risk to the project.

Timely payments are one of the largest factors in a credit score and if he hasn't had late payments since then, his score would continuously improve.

The most major factor in most markets is affordability.

is there a particular formula that takes all manner of factors, (employment growth, corporation development news, barrier to entry, rental rates, wage growth, etc) into account and spits out an "invest in city X" answer?

The ground floor is occupied by a commercial restaurant, and the upper floor is designated as SRO (Single Room Occupancy) under a pre-existing non-conforming use.