you're both wrong: The maximum normal STR is 13; tradeoff can bring it up to 15 (highest +2 before +3 16).
OP: I think it's a great idea, sort of.
use 2e. It's just better.
Keep in mind that the highest dmg bonus is +1; which means anyone avoiding damage must roll 16 (15+1 toughness save) to avoid injury.
HOWEVER this is only for rolls that involve saves. Skills can be as high as you like. Ditto Immunities. Ditto uncontested abilities. Flight can be whatever, I think... Super Strength also is ok, just not Enhanced ability (so you can life 40 million tons, but don't expect to do more than bruise with a punch). Ditto benefits (super wealthy! Super popular!)
At PL1 they're basically 0-level adventurers... well, commoners. This could/should be the story of how they level up. This is the level where they discover that Buffy is the Slayer, and that Sunnydale isn't the town they thought it was.
Higher-level monsters will be tough, but so long as their foes don't have damage-bonuses greater than +1 it doesn't matter who you throw at them.
Ever read David Eddings? This is the part where they're just kids who stumble upon the evil hedgemage's plot to destroy Loudwater! But who can they tell who'll listen to a blacksmith's fiery daughter, the bookish son of a cobbler, or their accident-prone pet wyrmling dragon? The old miller three farms over, that's who!
Consider using the XP tables for monsters rather than doling out a pp for each game session. You'll want to give them equipment (woo, a board with a nail +2!), which means a lump-sum of 15pp when the level up should work. Otherwise, it'll either take too long, or you're giving out PP in the middle of a session for every goblin they sneak around.
Letting them level up however works, but this would be the story of how they get their powers. Maybe one of them drinks a potion of Troll's Blood that gives them regeneration? Or another is transformed into a Golem? Or another finds a magical gem that lets them summon the Dragon-sword!
They can be non-standard powers, like super heroes, or they could be modeled after those of regular adventurers.
I think it's a good idea. ...you may have noticed that I tried to do it myself, but everyone else I told thought I was mad, MAD maaaaad! but I showed them, I showed the world! mrreeeehahahahahaaaaa!
You're totally right about this. it's a great idea for running the game, just make sure that whatever the bonus is, the average DC is 10 on the d20 (+modifier average). Keep things 50/50 and the PL isn't a big deal.