You are simply mixing up things:

You do not get payd per share. You get paid per shift based on the number of blocks found during that shift's "lifetime". It is quite simple actually: The reward for a shift is calculated by adding up the block reward for all blocks found during that shift's lifetime (let's assume 10 blocks were found resulting in ~25 BTC [before you start wondering: since at any point in time there are ten alive shifts the reward of a block is divided up amongst them of course]) dividing that by the total number of shares solved by ALL miners active during that shift's mining phase (let's assume 1,000,000,000, which leads to a reward per share of 0.000000025) and then multiplying that by the number of shares you provided(at 500 GH/s I'd assume about 42,000 which would result in a shift reward of 0.00105 BTC).

To cut that long story short: Since the reward you get is solely dependend on the number of blocks found and the fraction of totally found shares you provided. Combining Hashing power the way you propose yields absolutely zero gain over using that hashing power seperately in the same pool.

Another try to explain it simple: Let's talk solved shares instead of hashing power: Tim, John and Bob each are able to solve 10.000 shares per shift with their hashing power. Since the reward per share is calculated based on the found block rewards ot makes no difference wether they combine their hashing power or not, they still contribute only 30.000 shares together and thus get the exact same reward.

As was said earlier in the thread: the only possible use this could have is passing the auto payout minimum earlier, thus circumventing the quite large fee for manual withdrawels. But I am not sure if that is worth the hassle trusting the organizer (you) with collecting the BTCs and dividing them up amongst the participants of the operation.