An idea and a question

I was thinking about adding more flexibility in the Custom mode of the game. Today I played a Co-ops vs AI with a buddy of mine. Two players from our team afked right away and the poor Vayne that stayed got farmed in bot. I was playing Rengar , my friend was Kled and last but not least a

Basically it was a 3v5 against the bots and it was SUPER FUN because it was challenging. Why the amounts of players has to match the amount of bots in order to win IP in a game? I did get IP when the game finished because by chance people left the game but if I intended to have a 3v5 match (custom) I wouldn't win any IP at the end.

And one doubt I have is, here in LAS we don't have Twisted Treeline vs AI, does NA have it?