S'mon, you might be interested in my Lairs system - basically it's a group of monsters built with enough XP to raise a party of 5 at the Lair's level to the next level. A level 1 Lair has 5000 XP worth of monsters, for example. At a certain point I start treating monsters as minions, so high-level goblin lairs will have 300+ of the little bastards. (Minions are not included in the XP calculations.)
That's sort of in the 4e DMG under "Super Adventures", where they recommend each lair within the milieu (they don't say milieu) have enough XP to level up the party. I don't like that as a design parameter, I tend to think lairs should either be single-encounter or one night of play; the latter means about 1/3 the XP to level up the party.
I think the problem with treating the min-2 Rabble as novice combatants, the level 2 Bandit as 'trained', and level 3 Guard as 'experienced' is that the Bandit is the equivalent of 4 Rabble in combat, which is super-heroic by real world standards. It's as if every Bandit is the Grey Mouser, every Guard is a Master-of-Arms. IMO the power leap is much too great. For realism you would need to stat the typical peasant farmer as a level 1 Brute or somesuch, and not use minions at all.
Another way to look at it is to reject simulationism entirely, say that NPC stats only exist in relation to the PCs, and minions exist for dramatic reasons, not representing anything in the game world. In which case the GM stats a bunch of peasants as min-2 so the 1st level PCs can beat them up easy, or as brute-1 so the PCs can struggle with them in a muddy bloody knock-down drag-out fight, or as a high level Swarm so the PC Frankenstein can flee their vengeful pitchforks! I'm certain that's what WotC intend, but I'm a simulationist, it's in my blood.