the cloud, or the virtualization suits both pink and 2ch.
i can suggest 3 ways:
OpenVZ (free)
VMWare(non-free)
XenServer(free)
but one common problem is the I/O rate.
SATA II HDD that is now in use wouldn't have enough power and
probably would freeze up, for the speed of ν速.
maybe, you can change to the structure noted below for the cloud,
so it can be not so different from the one of 2ch.
Xeon Quad Core （3xxx series would be plenty.）
SAS or SSD RAID6 or RAID10
so much memory as possible(about 32GB？)
NIC ports have 4 ports.
it's affordable, like 1 million yen, or 10 thousand dollars?
bundle up all Pink BBSs into one machine
and virtually divide them into 4 pieces,
and you wouldn't have to change the current structure too much.
but, BSD would be waste b/c you cannot share the kernel on them.
so, i agree with your idea of having centos.
you can buy two machines and make them into (dangling structure?)
if you got money.
ネットワーク側ではスイッチに障害が出たときのことを考えBondingつかってフェイルオーバー。
Pinkのネットワークは外側から見る限り冗長構成取れてないんじゃ…
hosting cost would be more reasonable too. what do you think?