3 & 4 sound interesting, though probably impractical, backbreaking and perhaps unsafe (at least in getting it up there).

I never considered cold air returns to be quite as important as hot air registers - their primary function is to supply air to the blower and enhance distribution and mixing of conditioned air.

To test the effect of # 2, cover up return to be blocked with a piece of plywood or something and see what effect that has on warm air distribution. As long as the furnace seems to get all the air it needs from the adjacent return and drafty areas don't develop, you're probably alright.

I WOULD block the return being covered, however, perhaps with that same piece of plywood. If you don't block it, I would be concerned that the air current from the air return might oppose or offset the air currents generated by the fridge (i.e., suck air in the opposite direction that the fridge is trying to blow it) possibly causing to to overwork.

BTW, my back is hurting just picturing some people trying to get # 4 accomplished.

Ha, you're right. I'm thinking Superman.. or Superwoman. Thanks for the feedback!

I believe today's code doesn't allow for returns in the kitchen anyways. I think #2 is your best bet. You might want to add another cold air return somewhere else if you can, but I wouldn't worry too much about it.

There's another cold air return in the livingroom. Interesting info about the code not allowing them in kitchens. I wonder why?

Ok, I'm going to plan on moving the fridge to that spot. I'll block the air return with a piece of plywood or similar. Thanks.

"Interesting info about the code not allowing them in kitchens."

I do not think they are actually prohibited, just not recommended for the same reason you do not pu returns in bathrooms.

Do you want to blow ALL those smells throughout the house?

You miight be able to move the return out from under the refrigerator without to much trouble and install a weight bearing grate over a new return elsewhere in the kitchen.

Returns are just as important as outlets.
The air in the outlets has to come from somewhere.
Undersized returns will result in less air flow in the entire system and can lead to overheating of the furnace.

It should have enough controls to shut itself off without damage, but the heating performance will suffer.

If you have air conditioning restricting returns can freeze up the entire evaporator coil.

I’m curious what you ended up doing as I’m guessing that a return under or behind a refrigerator may actually enable the fridge to run more efficiently by extracting the heat off condenser coils.