Some things I see that hopefully can be incorporated into the site to really set it off!
In the theme teams section, especially for a hybrid team, have a way on the side to send that theme team to the lineup builder.
A VERY usable Wishlist! Create a way to add players to their wishlist and have that wishlist available as a sidebar when editing in the linup builder.
Off of above, when browsing any player, have the ability to send said player to your wish list or straight into the lineup builder. (second part not really needed if number 2 is implemented with the sidebar.
Been mentioned before, but we NEED multiple player compare options, BADLY!!!!
(not a big deal at all, but would be a nice thing to have) When adding a player to the lineup builder, have the team chemistry change option on the upgrade tab for power ups and such.