You make good points in favour of not changing the nature of the challenge, and I“m fine with it being focused just in reading.
My personal little issue with the challenge (or any) in general, and somehow why I had the thought of broadening it, is that I get very complacent as long as IĀ“m checking days. What I mean by this is that I will read something one day that lets me check that day, and call it done until the next, stopping my Japanese study almost completely. Which is not bad per se because Iām still doing something, but I feel like IĀ“m stagnating in other important areas of the language, i.e., listening, writing and the forever-forsaken speaking.
So I asked myself if this challenge is helping me achieve my goals faster (proficiency in all four areas of the language), or if itās āprocrastination in disguiseā. Now, I do think itās positively affecting my reading skills overall, and Iāve managed to increase the amount I was reading before by a lot. But at the same time I think I need to reconsider how I want to frame my study going forward. I think reading is a very important aspect of any language and I want to keep doing it, but Iām not sure if I want to put the entirety of my study time into reading.
Perhaps I could make it work nicely if I reduced the amount of reading that I do for this challenge (which, to be honest, wasnāt a lot to begin with, compared to what some of you beasts do :D) while adding other resources in the mix. Iām just worried about not being able to keep up with the challenge every single day, and become progressively demotivated as I see myself skipping days.
Iām so lost ;-; Iām not sure what would work best for myself. Ultimately I want things to work and push me to keep improving, but regardless I think I will join the next challenge. It actually feels selfish of me to try to mold it into what would work for me; I thought it was worth a discussion nonetheless! 
One thing is clear though and itās that I had a lot of fun with video games. Itās probably one of the most important drives for my interest in Japanese currently. Some can be very text-heavy and itās awesome when theyāre also voice acted.