If we're going to have speed creep rules, we should define the different "types" of Pokemon and what speed they're ideally going to run. Disclaimer: Yes, not all Pokemon will fit some role exactly, this is just in general.
Frail Sweeper: 252 Spe / 252 Atk
They aren't supposed to take hits, so they always run max Spe.
EX: Gengar, Jolteon
Balanced: Atk benchmark / Spe benchmark / rest HP/Def
This one's a little trickier, but this is one where Speed, offense and bulk are all utilized.
EX: BulkyGyara, Rotom-A, ChestoRest Kingdra
Bulky Offense: 252 Atk / minimal Spe / rest in HP
"Tanks", Pokemon that are supposed to take hits and hit hard back. Basically runs max Atk, hits a speed benchmark with like 20-80 EVs invested (or otherwise 0 Spe), and the rest dumped in HP.
EX: Rhyperior, Azumarill, Donphan (thinking UU here)
Walls: 252 HP / 252 Def
Pure defensive Pokemon. Doesn't run any speed unless it's fast enough to outrun a specific slower tier (8 Spe Milotic for example)
EX: Skarmory, Blissey, Weezing
With offensive Pokemon there isn't any problem, since they're all running max Spe or just enough to outrun other max Spe Pokemon. The problem basically comes up with the last two types, where everyone is running the bare minimum Speed. Basically, the rules as I see them are below:
1. Walls are required to run minimum speed, unless they have high enough base Spe to beat max Spe slower Pokemon.
Any wall with less than something like 70 Base Spe should always be running minimum Speed. The exceptions are with things like Milotic and Uxie, who are naturally fast and only need minimal investment for things like Max Spe Adamant Aggron.
2. Bulky offense Pokemon are allowed to run enough to outrun minimum Speed walls.
Best example of this is with Donphan running 84 Spe for minimum speed Clefable and Weezing. Since the Pokemon is offensive in nature, a few Speed EVs are more beneficial to it than to walls.
3. Pokemon can only run 1 point above a speed tier, not 2.
This means that we can't play the game of "Lanturn can run x EVs to outspeed Milotic by 1 that outspeeds Torterra by 1." Drop Lanturn's Speed down to Torterra +1, then say something like "The EVs outspeed Adamant Torterra, but many Milotic also hit that same speed stat... hint hint..."