I didn't review all the posts (new and old), but it seems if the second daylight photo shows your heat pump (photo also has the post with the small electrical box) - then your solution is to slightly expose the outlet pipe coming from the heater, and plumb the new SWCG in a vertical loop configuration. Outlet of the heat pump goes up a few feet, loops over, and on the downward leg install the flow switch and the SWCG cell, where it then mates up at ground (or a few inches into the ground) with the existing outflow pipe. Circupool for one actually markets a vertical install kit - although it is just the same pvc pipe fittings you can buy locally, cheaper, anyway. I did that last year with my above ground setup, due to space considerations. In addition, there would have to be a serious back siphon event for anything to get to the heater.
Worst case for the install is that you may elect to have a number of 90's installed to get the vertical loop to clear the other obstructions, so it may look a bit Rube Goldberg-y.
