Based on the rules from 2011 (as Al said), my interpretation is illegal.
However,
http://www.usfirst.org/roboticsprogr...ical-resources has a file called "Solenoid package" (a zip) which contains a PDF schematic. In it, you find that the solenoid bumper does just take the outputs and route them to headers.
Since it is done this way, I think it would be reasonable to allow replacement of this breakout by teams. I also think that it would be reasonable to allow direct wiring to a DB25, as a team could then build a multipin cable connecting the solenoid outputs to a valve manifold.
The way it is now (direct wiring outputs to solenoids), there isn't any real reason to restrict directly wiring to the solenoid module.
But that is my opinion.