It might be interesting if it were a class all of its own. You could limit it to inexpensive GWS fans to keep the speeds and cost down. Lightweight planes, especially if they're made from EPP foam, will minimize damage.

If you're trying to be competitive in an existing class of combat, EDF is definitely not the way to go. Straight-line speed isn't everything. Ideal combat planes turn on a dime and accelerate quickly. They don't call it "the furball" for nothing. An EDF plane might have a fast top speed, but turning bleeds off that speed, and the slow acceleration of your typical EDF would make you a sitting duck.

There's also the damage factor. Midairs are inevitable, and you can't build a plane strong enough to withstand them that's still light enough to fly. Props are $2. Carbon fiber fan units (the only way you'd be able to get enough thrust to be competitive is to use a top-of-the-line fan) are waaaaaay more than $2. When your plane takes a good shot, be prepared to get out your checkbook.