I agree with you @SirRandomChess , In the FFA league (4PCL), together with the organizers we have decided to use the time control 5 | 10, which has been a success, we have not had any complaints from anyone, and it seems to be very optimal for the 4 player game. It is the first time that it is used and it is on the right track, it would be great to have some chaturaji games with this Time Control 5|10 .
Does chaturaji as we play it actually make sense? Time control discussion.

wdym 10|15 is obviously too long? Its not really
Chaturaji blitz/rapid games usually last up to 20-25 minutes, and 10|15 games can last 40-60 minutes at least. How often do people even spend that much time playing a single chess game on the Internet? I almost never saw 10|15 in the lobby and it was played only by complete beginners who made moves quickly.
Perhaps now 10|15 is good for deep theoretical discussions, but not for regular/tournament games.

As for solo mode, it seems to me that this question is related to the previous thread about king=5.
I've looked at solo games in 4PC and there people easily sacrifice a 9-point queen to checkmate the king, get 20 points, and knock one of the players out. Example
I think that the main problem of solo mode in Chaturaji we saw in the final blitz championship match, when VEPOS and Terk had the advantage, but began to ruin each other and eventually won Fiat147, who in the last 25 moves had only a bare king.
If kings are worth 5 or even 10 points (similar to the 4PC), we can avoid such ironic results.
BTW, the Blitz leaderboard has 600+ players, the Rapid leaderboard only appeared for the first time in a long time (became 30+ players).
I find this illogical, so I'm all for making rapid great (again)!