So I figured I'd throw this out there, with all the changes I've done at this time, I'm comfortable saying that I have a fairly mobile, agile pool source that supports PPS, PPLNS, Solo mining, Backed by LMDB for share storage and processing. MySQL for transaction (Payment) data. This is running on a small variety of servers at the moment, but by and large, could be run on <40$ VPS' without too much of an issue, assuming they have SSDs.
Per-miner stats are complete, no-frontend for them yet, Mesh00 is working on that, and is doing a fantastic job with it, as he's redone: https://xmrpool.net, which is our running reference copy of the code. We've done tests out to 3-4 Mh/s on a E3-1270 w/ 16Gb of ram (2gb used) for our leaf/pool code, the majority of that pain is from the Monero Daemon, as the system runs at .5 load while verifying shares.
Per-miner notifications with Email is complete, integration with MailGun (Free for low volume, so ideal), means easy integration of other e-mail notifications. Custom payout thresholds are on the todo list.
I'm currently torn between FFS'ing and simply open-sourcing the pool (Both routes lead to this, at least eventually). Ideally, I'd lean towards FFS as I would like to implement more features over time at the request of the community, it's a fairly fun little project, and the Trunk/Leaf design means that pools have impressive flexibility to deploy remote nodes to any variety of locations, while still handling shares in a safe, sane manner.
Xmrpool.net uses this all as reference code, and serves as a living testbed for this work.