meni mentions greater risk for the op's style of payout if the pool has a larger percentage of the total hash rate.
the small pool of 1eh can only lose 318.978 btc coins in a year with a perfect losing record of never hitting a block in an entire year.
the larger pool would lose far more. with a perfect losing record.
So men's formula is but one guide to reserves needed.
I don't recall any mention of pool size in Meni's paper, also, i think pool size is not that important because of the variance, you are 100% correct when you say that larger pools will have to pay more than a smaller pool, but keep in mind the smaller the pool the greater the variance.
Last i saw this pool had less than 1ph of hashrate, while its true that he only needs to pay a small amount out of his pocket, he is likely going to continue doing so for so many years, with a tiny variance of 200% for the first block (which happens to all pools) he would need to keep paying of reserves for double the period.