I can see so much potential with this. If the Lua can be triggered on a RAM write, you could use a writebytetooffset in a pokescript to trigger a lua script, do some stuff, then return!
As for networking, that might take a bit of work for stuff like a DPPt style underground, but I can see some REALLY good but simple uses for networking: Mystery Gifts. Use an online distribution system (or codes based on an online thingy) to get certain items or event pokemon. Or, a GTS to trade pokemon with other ROM-Hack-players. OR, an online saving system where you can view your progress... With networking, the possibilities are endless!
Although, I must request one feature if it's not already existant: Linking (wireless or wired) from a Lua script. While it's possible manually, it's annoyingly difficult. If we could have link connections from lua, we could have a wifi battle system, or a wifi trading system in all the Pokemon Games!