New game mode suggestion

Nice idea, totally worth some attention!
There are many possibilities... and Lichess has already been improving a lot recently, so i believe that welcoming ideas and discussing them is a nice way to bring meaningful contributions to the community :)

* 5 different positions might be presented, each player would take (timed) turns discarding one of them, until one position remains; on a few seconds timeout, the selection would be random.

* After using Stockfish in low depth possibly to discard too unbalanced positions, some variation of Maia9 (human-like playstyle neural network built on top of Lc0; search 'maiachess' for details) might be a good alternative for evaluating how fair a position would be for humans to play (specially for complex positions; imagine a tangled mess of active pieces), and small modifications of the position might bring balance without having to generate everything from scratch again (given that randomly generated positions are often highly unbalanced).

* Random positions (instead of database selection) might generate fun games that wouldn't be possible with classical or fisher random chess, and the major difficulty would be on how to generate random positions that are human-fair and fun to play. Possibly a suitable task for neural networks, so this 'experimental variant' might gradually improve with user feedback; but surely it would take hours of coding and valuable computing resources, so it might just not be worth the effort.

* Game phase/complexity selection. Sometimes you're simply willing to train endgames (or anything), but the ones you face in your regular chess experience are obviously biased by your opening choices and playstyle, and also a large portion comes to an end way before reaching an endgame. So such filter might come as a valuable training tool, if not a source of fun and novelty by itself.

All of it would surely demand a considerable effort by the Lichess devs, so it might take a while to plan and think about implementing something like this. But they've already been bringing awesome news with the puzzles (database, dashboard, streak, storm, racer, and counting!), so my solid bet is that Lichess will continue to keep growing in many directions, and this one might pretty well be one of them. :D

@LeonardoBR I'm really surprised and impressed by the level of thought you put into this answer, as well as several other answers in this thread.

For me, it's only an idea that would have to be left to someone with knowledge like yours--or skills like developers would have--to implement.

The endgame-only idea was also suggested by another person. I think it's a good idea, and I've already seen in puzzles that they are being classified in this way. The game analysis postmortem board also classifies what stage a game is in, so perhaps they could do that with their existing database.

I am a little unclear how things go from an idea on the message board to an actual part of Lichess, though. Does it depend on a developer reading through the comments and then suggesting it at a developer meeting or something? My understanding is that the site doesn't have a huge amount of funding, so I will temper my expectations. Just curious.
Anyway, thanks for the feedback!

@laumothra
Interesting idea, but they lost me when they said nope repeat this process 100 times".

But yeah, in the playability aspect it wouldn't be unlike what I'm suggesting. The difference would be that these positions wouldn't be real game positions and so even if they are technically even, the chances of the one both sides Fair game producing an actual fun playing experience might be not that high.

#1 Before we get our hopes up...

1. This "0.5" is much more subjective than expected unless you're defining which engine, which version, how much time, which machine, etc. the number comes from.
2. There's already a way to play "thematic" tournaments, for example lichess.org/tournament/tbGcInhz

@Toadofsky true, there's some details to iron out. Seems like the more analysis is done to a game, the more likely you are to see the advantage that one side has.
One way to look at it would be that players would have around 20 or 30 seconds to make their first move, so we wouldn't expect most people to figure out a multi-move combination that leads to a benefit. Seems like using one of the human-like stockfish would be good, but this part is way over my head.

I think it's different than the tournament options because it would be more like a random position rather than a set opening. You could also use positions from chess 960 games. Also, one could just jump right into a game rather than have to go through the whole rigmarole of a tournament

#15 Yeah, again I like the idea...

Years ago developers considered whether or not it was worth keeping thematic (from position) tournaments; I argued strongly in favor of keeping them for all the same reasons we are now discussing; plus they are a training tool for competitive teams used at high school and collegiate levels.

I don't foresee this proposed option being accepted this decade; Lichess contains lots of source code and thematic games already serve a similar purpose.