Scratch 100x 1Mkey/s miners.

Use one big gpu farm then,

One could likely write a script that generates a thousand or however many Bitcoin addresses saving private keys of course.

Then point the farm to miner on your pool with each address until each one finds a share.

Then the reward keeps going down and down per share, but really that one gpu farm has all the shares...

Boom! even if it was just 10% of the pools hash rate it could take all the profits.  Because that other big hash rate gpu farm doesn't get but 1 share per 30 minutes because they are playing fair.

Then its pointless to mine if profit was really ever there...

I'm sure sweeping the coins from generated share stealing address would be a breeze too, easier than stopping miners after one share.

But I'm not being critical in a negative sense, its an awesome idea and I wish I did it first.  :-D

Good job so far!

PS: A server side only solution would be the best option of perhaps resetting the variable for "share already solved" to zero after adding a share to stats.  Don't know the server side code, is this possible?  Sounds too easy...  Anyways, pretty exciting stuff.  Only problem with a custom oclvanitygen is windows users struggle compiling it from source and the trust factor for new precompiled forks is low.  I would certainly add your mods to my fork though, but would need an additional flag for setting options for your pool as not to mess up compatibility with any other pools that may exist.