So you still haven't answered the question regarding what happens when the enemy has a strong counter jungler and just steals your red.

Also, I'm okay with the idea in principal, and it's certainly an option for ranked teams where there's a high level of trust on the team with what your teammates will do with the buffs, but what happens if you put blue buff on your teammate and he nearly immediately feeds it to the lane opponent?

Now your teammate is behind. You're out a blue buff and experience (making it harder to help your teammate catch up), and the enemy jungler can pretty much ignore that lane and put extra pressure on the other lanes.

Then the enemy Jungler has your Red. That's all. It might give him a little more gold and exp, but it doesn't really affect Mundo. Buffs are important but there are many more things to consider in a game.

Yes, things can mess up. What if your team is winning 50 kills to 0, but then you go in one at a time, die one by one and the enemy team wins? Some times, a team might make a stupid mistake and throw the game there and then. Some times a team comp strategy that works on 9 out of 10 teams might be countered by a specific team they were paired against. Such things happen, but if it's a generally solid strategy, then it's a good one.

(I.e., many people follow the Top, AP Mid, Support ADC Bot and Jungler Meta. Doesn't mean it works 100% of the time, but it's still considered "good".)

You're ruining your own jungle in the hopes that the person you give the buff to can stomp their lane down. This isn't always the case - a lot of people get overconfident with an early blue, and promptly get ganked and lose it.

Best case scenario, what you want to happen actually does happen. Usual case scenario, it's enough to give them an edge but not enough to win the lane - meanwhile you're out on a big amount of xp and behind. It's not really worth doing and it weakens your ganking and counterjungling ability.

And yes, even with Mundo. Just because he can clear quickly doesn't mean he doesn't need to get exp to stay in the game.

Admitedly, this is a strategy I'm designing with low ELO players in mind. Low ELO players who many not know how to handle a Blue-buffed ADC at level 2 from the get-go. Low ELO players who, sometimes, crumble as soon as there's a disadvantage. Low ELO players where there is usually a significant degree of disparity in skill somewhere on the map.

I don't think this will be quite as good a strategy for, say, Diamond Play or whatnot, but at lower ELOs, I think weakening the Jungler is worth it if it strengthens a lane in return, because the Jungler can avoid confrontations that aren't in their favour. Laners must deal with opponents who are in the same lane.