Disconnect penalties will not "ensure" that no player will ever leave for whatever reason. Quits will still happen.
Look, in the games I play the absolute overwhelming percentage of the time quits are because of rage or connection issues. Rage is being dealt with; throw that out the window. Connection issues are also being dealt with (global fixes, ban players with known problems in your list). So all that's left are "miscellaneous" walk-the-dog type of quits that happen so insignificantly they aren't worth attention at this time IMO.
But it is a problem at this time and as already pointed out, there is no certainty about whether or not the upcoming changes will reduce the amount of quitters so significantly, that it won't be a problem anymore. All you are saying right now is, that AI farming is fine.
I am not saying AI farming is fine; I'm saying this is hackish band-aid solution to a problem that, as you've stated, we're not certain will be nearly as pressing an issue once existing solutions are deployed. We can reevaluate at that time. When they do reevaluate, most likely they will implement the non-hackish intuitive more direct and customizeable solution I provided.
My suggestion is, if this is really something you want, is that they should implement an AI handicap option (either kill reward, health, or an option for both). Setting it at 200% means AI's get twice the health or gold reward or whatever, 50% means half. This way, since it's a clearly-visible setting in the game options menu, it is exposed to players rather than being an arbitrary game nuance that must be discovered manually. This would require interface changes and more than a few lines of code and testing (so again, not worth it atm IMO) but at least this is software development done right rather than gameplay hacks to appease whiners.
It also enables more options for skirmish games. Can you win 3 humans vs 3 AI when they have twice the starting health? Can you win 1 vs 3 AI when they have 50% health? It's useful in more places and it's more intuitive. It's software development done by someone with an ounce of foresight.
<--is a proponent of skirmish options in a skirmish-style game... see my "why can't we play 4-player FFA" thread