Tubifex (as well as cyclops, daphnia and copepods) are great live food that fish can find, and can survive (seeming no matter what) long periods without being actually fed. I have some in with a cherry shrimp tank, they were in the substrate from when the tank was full of fish. I only feed my cherries once in a while, but keep almond leaves in the tank, so they must be eating the almond leaves as they decompose.
It's not a great idea if you're only going there once or twice a year, but if you go there every month, I see no problem keeping the right fish in there.
The temperature is another thing entirely... If it's getting 90+ in there, you're not going to be able to keep much of anything alive, including copepods and tubifex. And with pumps going through the ground and such, there's a lot of things that can go wrong. First off, if it's 90 degrees in the vacation home, and 70-75 in the tank, you're going to have massive condensation on the tank, which means the stand, the floor, the walls will all start rotting and getting moldy. Bad situation, but if you're there in the summer, with AC on, or have fans going in the house all the time, it would be less of a problem. Then there's the problem with evaporation... Regardless of having covers on the tank, there will be evap. In summer months, my 55g with glass lids will lose 3-4 gallons a week, that's with the temperature being 90 indoors, tank temperature 78. If you have really good buddies that will top off the tanks and such, that would be nice. But I see this tank idea being a ton of trouble.
If you spend a month or so there in the summer or whatnot, maybe you can transport paradise fish or bettas, or gouramis or other labyrinth fish there and back... Keep the tank up, lights on timers, seran wrap the top of the tank while you're gone to minimize the evap, then do a water change when you get there, and toss your fish in there while you're there, then transport them to your home tank when you're home.... It's a little trouble, but sounds like a lot less trouble than trying to maintain a tank remotely for months.
Anyhow, I envy your endeavors!