All this sounds great tbh, remove all the broken things and make it more competitive. I normally play ark on console but might actually play it on PC for this mode.
Meaningful changes to improve the map would be great, also keeping in mind how solo players play and make smaller defendable positions, possibly even making the maps bigger. Getting rid of shared experience would also be great because players working together already have a massive advantage.
25 players max still sounds way too much. I'd honestly welcome 5 man tribes. I can only hope.
If this game never had the huge tribe numbers stigma and people expecting tribes to run for eternity as a breeding simulator I honestly think it would have had huge potential.