You can build a local boot server that provides the IP and kernel. LTSP
can then be setup to point to a remote X server. Keep in mind that X is
a pig: expect the remote thin clients to run slowly. This can be
improved greatly with No Machine's NX server and client (or freenx on
the server end, if you want to go the GPL route). The NX server would
run on the remote X server; the NX client would run on the thin clients.
One other thing, if your link between the two sites is slow, booting a
thin client, not to mention several, will be slow too. A fast
connection won't be much better, especially when compared to a local
network.
HTH,