Our bigger issue is that the leaking water separate my house's slabs and soil underneath it, a huge cavity was formed under my house.

The builder is DSLD homes, he is building this as part of a >200 building neighborhood, seems by all means reputable, but I am also learning that foundation failure usually has nothing to do with the quality of the construction and more about the underlying soil content. 

If the lowest grade can be raised to the BFE or higher without violating residence codes (most require soil be a certain distance away from your lowest floor to prevent moisture wicking, rot, critters, and termites), then you may be eligible to get an exception from FEMA called a LOMA - if you are successful the LOMA essentially states the property is out of the flood zone and you will get normal flood premiums.Summary: Government backed loans require the buyer to use FEMA premiums for flood zones, they will be high, and cannot be shopped through private flood insurance.

Some towns like Sandy have ordinances restricting AirBnb.

I don’t think indoor pools will be a good idea unless it is some multi million dollar estate or those expensive deals in NY city.I had to remove the bottom of the pool to allow drainage and then back filled with approved soil with compaction reports and geologist oversight and stamped approvals.

Soil was analyzed and did not exceed CT''s limit of 500ppm.The seller has already refused to remove the oil tank.

There is an REIA meetup Thursday at Club 90 in Sandy.

Lastly, if the lots are not going to have city water/sewer and would need well & Septic then a soil scientist might be needed to tell you where a well/septic could go which might affect the lines the surveyor cuts.

I sold the property as is, didn't remediate the soil.

Maybe one pathway is more desirable for a reason you do not understand, they like left turns more than right turns, the soil is better packed, the soil drains better in the wet weather, there is less slipperiness in freezing conditions, the plants look nicer, they are further from the neighbor they do not like, they are just used to walking that way, they do not like your plans and want to stop them.Since they are the same, why not design your changes so that they are the mirror image of what you are planning?