One addendum that is included on the lease we do is an early release addendum. 

That their noise should not be extending past their walls.

What I would like to do is utilize a tablet or something so that I can craft a unique welcome letter for each specific guest.

That removes you one more degree in the corporate veil argument and doesn't leave you hanging liability wise with the properties in your name for an extended period of time.Beware that there are some state issues with this as it relates to community property. 

I have a property that will have a balloon payment due in < 2 years and I want to refinance it to at least extend the term.

If I wasn't an agent and going to buy a property from a seller's agent - me (they buyer) still have the right to ask for option times (7-10 standard) or extended (14 days+), be able to assess rehab/costs, and have the option to move forward or not.

Has the Mortgage Debt Forgiveness Act been extended?

If they are not able to work with you to extend the 45 day deadline then it sounds like they would be a pain to work with for any issues/claims in the future. 

Do you just go under contract and then in diligence work towards extending some of the leases?

I see you basically competing with some sort of extended stay hotel.Hope this helps