Top u23 players who are outside of the first team squad often drop back in to the WP when not required. The drop in quality is too great. The diversity of coaching and approach, combined with the issues of not training with the WP team, all on top of the disruption caused to the WP team, means that an u23 team would best suit the needs of all.
The WP needs to be independent to be strong. There are players like Thomas Young, Cory Hill, Matthew Screech or whoever, not kicking on because they are not good enough for the first team but too good for the WP.