Before I begin my explanation of my solution to your problem, it first needs to be established that the 4th Edition level system is RELATIVE, not ABSOLUTE. By this, I mean that the only thing that really matters is the difference between your level and the level of the other guy, and that otherwise, the math should be even. According to the rules, you should almost always use equal level opponents. As an experienced DM, I'd extend this a little and say that, at the very most, use opponents who are no more than 4 levels above or below your party.
There is a sneaky and subtle solution, however, if you're willing to homebrew a little bit. It's never stated outright in the rules, but it can be derived from the rules, that you can adjust a creature's level in two ways while still keeping them at the same "thematic power level". By this I mean the math will work out in combat for a fun game, and the players will still feel like the opponent is of the appropriate relative power to themselves, which is key.
If you need to increase something's level, you can either make it a minion, or you can put a bunch of them together in a swarm or mob or even an army. In either case, increase the level by 5 each time. (To go the other way, and face an opponent much higher level than the players, you can drop the level by 5 and make the creature elite, or solo)
If the players want to mess with an entire room of villagers, I would treat them, together, as a single "Mob" creature, of level 5 (or 4, if you want to be technical and claim that villager are normally level 0). If your players are higher level than that, then make the mob a minion of level 10 (or 9, ibid). This is perfectly fair, and even makes sense thematically, that a level 9 or 10 player character SHOULD be able to take out an entire room of villagers in a single attack... they're just that awesome.
If your party is in the middle or upper paragon tier, then villagers simply won't be a combat factor, any any combat abilities the players want to use are simply going to work, every time... unless you want to increase those villagers to an entire army. Say, instead of a room full, we're talking the entire village of 100 or more at once, as a single creature. You'll have to eyeball it, but I could see 100 villagers warranting an upgrade of 10 levels. You'd still need to make it a minion creature to get the level up to 15 (or 14) of course, but at paragon levels, this still makes sense.
If you need to go epic? Well, your army will have to get bigger. An epic character could likely handle 1000, maybe even 10000 villagers as a single creature. "How will all those villagers fit into a 4x4 square?" you ask? Well, you increase the "size" of the square from being 5' squares to much bigger squares instead (I like old school 10' squares for paragon, and 100' for epic), implying that the character has enough speed and skill to "control" a much larger tactical area.
I highly suggest you try this out. It really works for conveying the right "feel" for these encounters, while still providing an actual game to play where the dice do matter.