I am suggesting some alternatives to replaces leaver heroes with bots, because I believe (after playing 2 games consecutively with bot-leavers within the first 5 minutes) that bots are way too easy to repeatedly kill and harvest massive amounts of gold from. In essence making the game even harder than a 1v2 or 2v3 from all the fed gold and experience.
1. Split all the accumulated wealth and item value between the remaining players (or some fraction of said wealth), and then remove the hero entirely. This is similar to the dota system of replacing leavers, and it has worked well for DotA. Not to encourage becoming a dota clone, it just seems to function well.
2. Make bots worth much less gold and experience when killed. This way it isn't as much of an incentive to farm the bot heroes, and the lone hero or disadvantaged heroes do not get beaten worse by heavily-geared advantaged opponents.
3. Completely remove the bot replacement function and do not give any gold out or any assistance to remaining team mates. At this point it is more beneficial than having a bot player.
Edit: I should mention, all other possible changes to the current system you wish to present, please just post them beneath. Any other feedback on my ideas also feel free to post about.