Looking into something else, found an issue crops up.

I have 2 QBs on my roster; both have ratings listed, QB1 in QB and RB, QB2 in QB, RB and bizarrely LG. As a consequence they can only be converted to those positions.

I drafted this WR, https://nfl.myfootballnow.com/player/16622 this draft - can convert to RB, WR or TE.

I'm not going to get into discussing his skill ratings or how it's determined which positions a player can play, more the data generated pre draft.

The WR as I've shown appears in all position filtered CSV files. Select QB, players not in position check box set, he's shown. There's a slight issue here in that he and other players would appear in player files for position they can never be converted to.

Using this example (and can also be extended to Free Agents), can a player ONLY show up in searches and downloadable files IF they can play / be converted to the position being filtered on. This would remove a lot of noise from the search results / csv files.