User blog comment:Frodo the 9 fingered/A Third Camp?/@comment-5112532-20120731101113/@comment-3146930-20120731103253

The problem with that is right in your comment. The gods don't want Greeks and Romans to mix. If a Greek demigod almost mde it to Camp Jupiter, the gods would do anything to make sure it didn't happen. I mean Annabeth lived in the area of Camp Jupiter for years and never once even considered the posibility of another camp as the Mist was too strong there.

Also, going by page count the Mark of Athena is the longest book in the series yet. It may not be too late to introduce another character or camp, like a big reveal at the end or middle or something. As far as a patron, these demigods are still children of the gods. I don't feel that the gods would ignore them. I mean Camp Half-Blood had a bronze dragon before they had a strong border so this camp most likely has some level of protection.