Minecraft using player score as a variable

In a map I'm making I have a command block loop, and for every time it loops all players speed increases by 1 tier. Anyone know how to do this?

While being able to take a value from a scoreboard and use it as the tier of an effect would be nice, it is impossible without using many command blocks (one for each tier).

I'll give an idea of how I'd do it:

It's nice and easy to increment scoreboards using

/scoreboard players add @a <scoreboard name> 1

You could use a dummy player instead of every player, but doing it this way, you can exclude players (maybe when they die, or when they do, they're speed is reset).

Then in a bunch of command blocks (in 1.9 chain command blocks come in handy) put in each block:

/effect @a[score_<scoreboard>_min=<x>,score_<scoreboard>=<x>] speed <seconds> <x>