I have been interested in Pauper of late and wished we had alternatives to "come into play tapped." Pauper is obviously a slower format, but I see Pauper as Legacy lite. "Come into play tapped" will slow the game, but I think Painlands e.g Brushland can be modified to common to offer an alternative play style.
I don't know if these can be common in a modern set, or even a supplemental-level product. The bar for common duals is ETB tapped because of the sheer power associated with such land entering untapped, but pain and ETBT simply aren't equivalent downsides. I can see pain-only duals at uncommon, but ETB untapped duals are just so strong that there isn't a good corollary drawback to entering tapped that would justify common rarity. It would be like trying to put a Wasteland variant or a manland at common.
Easy fixing, in WTC's eye,should be hard, and the easier it is, the rarer it is. 1 damage per pop isn't hard at all, compared to coming into play tapped. Damage simply can't be equated to the lost speed.
The limited environment will be hurt badly by this. You see something good, just take it without really worrying if you can cast it or not.
Common pains - really, common any-dual-that-doesn't-ETBT - can't be done. That's for both complexity and power reasons, cutting both ways: Nobody wants to draft a bunch of common ETBuntapped duals, have a stupidly fast Limited environment, and occasionally lose because they paid too much life to their painlands.
The most you can get out of a common dual is ETBT and small upside: Gates, lifelands, things like that. I agree, however, that pain-only duals could be uncommon.
The real problem is you are too generous to players. You see, MtG is all about the gambling / lootbox effect. Putting good, desirable cards at common would undermine the entire booster addiction that revolves around chase rares.