Alright, I've finally tackled Champion's Road! I did it not once, but twice! I did use multiple controllers like I said I would, but I still find switching controllers hard, so I just stuck with Peach in a Tanooki Suit, which I stocked up on from World 3-1 (earliest level with this power-up).
The reason for Tanooki Peach is obvious: reasonably long air-time. This is very important for two sections: the beat blocks and the dash pad section. Even after tackling the beat blocks section as normal characters, I can't, for the life of me, figure out the way to do the last beat block section (the last four blocks are the main culprit). I did the second last part by sacrificing Peach by throwing an inactive character to the safe platform. The dash pads one is the part I failed quite a few times, and at one time I didn't recognise Peach from the other characters and unknowingly suicide her to the abyss. When I reached near the goal, I have the utmost relief from all of this,
It took several attempts to do this, and whenever I am out of Super Leaves, I just close the software instead of exiting, since this game saves when I exit normally (which I don't want because gathering power-ups is a hassle). This is unlike New Super Mario Bros. U, where I can quit with power-ups intact (I wish I don't need to close in the middle of the game to reset the power-ups).
For the first time, I used Mario, Peach and Toad. When I got to the end goal, I made Mario a Tanooki and reached the top of the flag pole, then quickly got Peach there too. However, I panicked and reached for the wrong Wii Remote (I had two ready with me, but one ran out of battery) and missed Toad's control. For the second time, since I got the top-of-flagpole bonus already, I could use the easier way to grab the flagpole: throw inactive players with one of the characters I missed (in this case, Toad). I threw Rosalina and Luigi, then grab it with Toad. In the end, I got all five playable characters' icons for Champion's Road, and boy was it a relief to do it, so that I or anybody else don't have to complete that stage again!
Now my next goal is to complete the Mystery House Marathon with other characters besides Mario (since I completed it with him only). When that is done, then it's Boss Blitz for all but Mario (again, completed that with Mario only previously). After that, the others levels should be easier to complete, and thus, become a more relaxing affair.
Thanks for reading.