I'm honestly not to fond of the idea. They should atleast work out the server stability issues (preffarbly some of the other bugs while they're at it) before opening another server. Especialyl when you consider that this won't be a test server but an actual server that will need support, moderating, and considering they plan to bring in customs also (well more obviously.. and custom mobs seems to be a universal pain in the rear end no matter what kind of server you run) they will have more stuff that can go wrong there and they will need to spend more time balancing it.
So, fix what you got before you start new stuff, you don't impress anyone by having 4 buggy, unstable servers when you could instead have three stable servers with minimal amounts of bugs.
Ohwell the e-penis syndrome strikes again I suppose...