As an alternative to disabling functionality (that you might need later) I would suggest separating the networks, so that LMCEs DHCP only controls the relevant part of the network, but the DNLA TV and Playon is kept on the "outside"...
(let me try to draw a map, perhaps that's easier)
Internet --- Gateway (local router) ---- Local net (outside LMCE) ---- LMCE Core -------------------- Local LMCE managed net
Example IP configuration:
All IPs /188.8.131.52 192.168.1.x 192.168.1.200/192.168.80.1 192.168.80.x
Router DNLA TV (192.168.1.10) MD 1 (192.168.80.40)
Playon (192.168.1.20) MD 2 (192.168.80.41)
SAN (192.168.1.2) Weborbiter (192.168.80.42)
You would need to enable LMCE autodiscovery to "see" the SAN share - or alternatively put the SAN inside the LMCE "domain" (i.e. 192.168.80.??) and then forward relevant ports/services enabling the local-outside units to access the SAN...
And then be aware of where you place other units (PCs, iPads, Printers, etc.) - some forwarding/mapping of ports could be needed when units are on different local nets.. But a few simple rules should cater for all