The problem with known, non-random openings is that engines can be tuned for them. So if TCEC gets significant level of popularity, authors might consider it worth tuning. By using predefined openings, better tuned for a specific openings, but not generally better engine could win.BB+ wrote:Another option would be to query outside expertise. There's got to be some quality book-makers around who would be willing to spend the time (3-5 hours?) to collate 56 (times 3, plus a few more for the Elite match) playable opening positions for a season's worth of games, especially now that TCEC has gone big-time. I don't see how this could fail to improve on random PGN selections. You could also open it up to the public via a poll somehow.
I see this as a much more serious problem than maybe slightly unbalanced openings.
Edit: The good example for this is Rybka and Noomen suit for which Rybka is tuned so it gets 30 Elo better performance than with a proper non-tuned suit.
I can't imagine an author caring too much about tuning to a "TCEC book" (is this more likely than aiming for wins in the 3:1:0 system via artificially increased contempt?), though I agree this should simply be made essentially impossible (unless there's a leak).
There was also the RobboLito 
Obviously it's only 28 positions per Division, as each position is played twice. I can give some more specific criteria as to how I would choose such positions, though others are likely to be more competent with this. A lot of the minutiae would depend on your goals in any event (for instance, breadth of openings, recent popularity, drawishness..).