IDs for all things are restricted on the HTLauncher code, the code define each range with a START and END, that definition is on the code, not on the xml files, that is why when you reached the MAX for CHARACTERMESH_TMD which is 10999 and for example you add another one with id 11000 client will crash or ignore that ID, now if you add 11001 most probably is that your client will crash because 11001 belongs to the NPC_TMD and is already on your xml on the npc tab declared.
So to add more IDs for the CHARACTERMESH_TMD you will need to hex edit the HTLauncher, with one of the 2 options I mentioned in my previous post.