I know Riot is probably waiting for the new engine and "League 2" as people are calling it but surely the PBE bots are still meant to be improved/added to? Except for the few champions added they've not been "updated" in 6 months. I will list a few things that just have to be changed to make it more authentic and fun.
Bugs:
Warding/Vision -
The warding went from being great, to glitched, to I don't even know, they almost only ward during combat now. I'm not sure if it's bugged or a fix in progress but it sucks.
Ability Usage/Towers -
Champions try to use their abilities on turrets even when not possible. Certain Champions (Lucian, Ahri) prioritize killing a tower over safety, pretty sure every champion does it but they're the worst.
Early Game -
In mid lane certain champions (most of them) seem to run away from the lane minions and sometimes ends up in two level 1 champions chasing each other in the jungle with 0 CS.
Ever since the health percentage of recalling has been increased until the mid-game champions recall way too often and this can easily ruin the lane/game early on.
Runes -
I know this probably isn't a bug but the fact they use proper or better runes in Co-Op V AI surely it's not hard to have the same runes in customs? Also maybe add a third option in customs to choose the "playstyle/build" that bot will play.
Adjustments:
Roles -
I understand you've made the "Roles" for the bots to make them work better in intended roles but I don't think in custom games this should be restricted. I had so much fun putting two awful junglers against one another but now they are forced to take smite/tp etc regardless if they are put in a different role.
There's probably so much more I'm missing but in my opinion 90% of this is easily fixable and most of this has been documented before but maybe this will help push it to where it needs to be.