In the end, due to the "great news" they found, they ended up not installing an overhead sewer line or digging out front to attach the downspouts to the mainline in front of our house, but instead, redirected some of the existing piping and doing an edited version of the proposed plan that more heavily used the intact mainline under the house.The end result has seemed to be a resolution to the problem (so the ultimate purpose of the work was achieved), but with what I would estimate to be about 50-70% of the total proposed work.

I believe what you are proposing means jail time 

Depending on where your proposed aggregate rate falls, it may be a no brainer to refinance and fix your rate in. 

One such similar examplehttps://www.publicspendforum.net/blogs/steven-koprince/2017/11/03/gao-email-delivery-receipt-didnt-confirm-proposal-submission

That’s the easy part, now you have to get the lenders to agree on the proposed Net them from the sale. 

Could he simply propose jacking the HOA dues so high to force the rest of us to sell to him?

BiggerPockets also has a "Tools" tab above, hover your cursor over it and click "FilePlace"... here they have templates and documents that you might be able to search through and find what you're looking for.Once you have the LOI (otherwise known as an offer binder, offer sheet, deal sheet, etc), all you have to do is outline the terms of your offer: Proposed purchase price; deposit amount; total down payment; method of payment (cash, mortgage); contingencies (inspection, appraisal, etc); proposed contract date; proposed closing date and anything else outlined on the form or anything else you'd like to include. 

Since you are making this proposal to an investor, first think about reasons he/she may be interested in not owning the property anymore.

They work because the property is pre-appraised to its future , finished value by showing an Appraiser the contractors proposal with all costs and updates to be done.

There is a huge vitalization planned there and a proposed Brewery that has already got a lease on a building.