My opinion only 2 cases make sense for the seller 1) they have few options and this presents the best means to get out if a bad situation.  

You aren’t owners with lease options.

It sounds like you're in a pretty good position with some nice options.

Happy to talk thru options for what you are looking for!

With no direction from an Engineer (or Architect) Contractors have no idea and will price out the scope of work they think is best even if it's not the best option. 

once the loan comes due for a bridge loan what are your options?

I’m considering two options to present my plans: 1.

Another option is to put 2-3 inches of spray foam insulation then batt under that, it will assist with stopping some of the air transfer and seal it off as well.I would also check the windows in those rooms and whcih way do they face.

If you want to find out how much equity you have to see if that’s an option for you, connect with a real estate agent and ask for a professional equity assessment report (PEAR).Who knows, you may find out you have enough equity to buy your next place outright– and with today’s mortgage rates, not having to take out a home loan is pretty incredible.

I am acutely exploring new construction options in NC right now, I would love to connect it seems you have a lot of know to share :)