I like this suggestion for other reasons:
The first or first N posts, is the perfect time to tell the user if he/she has choosen a bad board for their question, and give guidance on why this is so and how to choose it next time. Also the [code] [/code] can be explained. Crossposting would also be caught, and likewise the URGENT NOOB .... well, frequent posters know what I mean.
Why would they listen more to advice with this than before? Because their post does not get published until they acknowledge !
The work of the auxiliary moderators would be a simple [reject-spam] or [boilerplate about xyz] where xyz is the above very common problems of 1st time posters. So it should be no more than a few cut-n-paste of the usual links (to the GammonStickies, subsections).
It is not meant as an absolute filter, just a little extension to the spam-filter function as Jack suggested to remove some of the obvious 1st post error.