Neither would we want to spend our money on something aesthetic at this point.

Best thing for stopping this problem permanently is removing the tree (aesthetics and city laws notwithstanding). 

Heat pump units are more efficient than window or portable air conditioners, more aesthetically pleasing.

Was there a specific reason - aesthetics, trying to use up space, (not sure if "the land and asphalt all add up by adding 10 ft" fits here), etc.?

If you're at all good with aesthetics and brand you can build a tiny house bungalow or renovate an airstream.

The last thing you want to have to deal with is spending money to improve the overall value of the property, and then minor aesthetics and details are missed, which add up; ex. painted over light switch plate covers, or stairwell railings which have been painted over several times and never correctly sanded down, etc - gives it a look like it hasn't been done correctly and can decrease the value of the place.

I go by aesthetics of the unit. 

The only other reason for a dock would be aesthetics and fishing, which I think would add marginal value at best.

And for rental, is that picking it up cheap, like on a wholesale deal, minor rehab, aesthetics andthen renting it with an roi after expenses at around 8 to 10% if not more?

Not only are they not aesthetic, they have all the issues you mention.