One or two engines on their own, fully agree. That makes very little sense, especially the tiny ones from an economical POV. But what does make sense, is having ALL engines run on the same fuel. No more different fuels to bring along, no more big and heavy fieldboxes.

I remember back in the days when still flying glow, bringing 2 or 3 different fuels to the field depending on which set of models I brought. Then I would need a 30 lbs fieldbox containing 1 3/4 gallong of fuel, batteries, starters, tools, rags, cleaning stuff, spare plugs and what not..
Now I bring a tiny 5 lbs shoebox sized toolbox, one can (1/2 gallon) of fuel regardless of which planes I bring, and a small pack of wet wipes. No rags or cleaning agents. Simply because everything now runs on the same fuel.

That makes sense.