Is it possible to move a filter from one side of the pool to the other on an above ground pool. I would like to install a heater but the gas line is on the other side of the house and a deck is in front of the pool. We would have to run the line under the deck.

Yes and no, are you thinking of moving and patching the old skimmer hole or just using two very long lengths of hose to reach half way around the pool? The later will decrease your flow rate.

I am looking at any option. I was told today that it shouldn't be done. If you patch the hole and make another one, it might affect the stability. If you put the pump on the other side and run a hose over to the other side, it would be very hard on the pump and also affect the pressure.

The long hose would reduce your circulation and that has a trickle down effect on the chlorine, filtration and even the heater. You can patch the wall but it will show on the outside and you will have to replace your liner. I would just buy a proper length of CSST Corrugated Stainless Steel Tubing (CSST) for Gas Distribution (http://www.toolbase.org/Technology-Inventory/Plumbing/corrugated-stainless-steel-tubing) and put the heater over by the pump. The pipe is not cheap but much less work, no patching, circulation is maintained.