No, you cannot place a WAR within a WAR. Each WAR is a stand-alone entity and its structure is defined by the
J2EE spec - which among other things says that certain files and directories must be located at certain absolute places within the WAR file. Exploding the WAR file into a physical disk directory tree doesn't change that.
But what you really want is to provide 2 different contexts, where one context path is and extended version of the other context path. Since each context can locate its WAR anywhere it wants, actual physical embedding of a WAR isn't required.
The real question is "can
Tomcat be directed to match first against a longer context path, then fall back to a shorter path if the longer match fails?". I don't know. It might even do that by default, although I'd have to RTFM, or maybe even the source code.
Assuming it doesn't, however, an alternative would be to employ a URL rewriting scheme so that, for example www.submission.com/submit/test remaps to www.submission.com/test and www.submission.com/submit (without the "/test") passes through unchanged.