Have a future home site in the country.
Would like to have a well and septic put in to use for the house and now for camping.

Is there a secure way to tie into the well and septic systems on a temporary basis for camping and then secure the systems from people and weather damage?

Build a small shed for a toilet and sink. Later, once the hopuse is built, it can become your tool shed

I think your question really is "How can I stop people from stealing my stuff?".

The answer is you can't, not if they have enough time.

I doubt that anyone would steal you septic tank and system. It takes too much work to dig it up and it would be easier to steal it from the building supply. You can easily rig up some kind of quick connection for you camper.

The well is a different story. They aren't going to steal the well per se but they will steal the pump and every thing associated with it.

If you have an above ground pump you could take it with you. However, if you have electric service to the site they will steal that equipment. They will certainly steal the breaker panel or disconnect. It's just too easy to cut the meter seal, pull the meter and take the panel. They very well may even steal the entire pole. Not that hard to cut the service line with a pair of insulated bolt cutters.

If you have a submersible pump at the bottom of the well they may get that. It's not that hard to pull a pump on the end of flexible well pipe or PVC. Probably take 2 people about 45 minutes since they don't care how much damage they do to other things.

You best bet would be an above ground pump, such as a jet well pump and a generator that you take with you when you leave.