I have no idea if it's too late in the design process to implement something like this, but I'd really love to see an alt alphas kit that's the same color as the mods. I love the light orange on the cool/dark grey and to be able to put together a mod-colored monokit would be awesome.
I think alt-alphas would also increase the sales of accent spacebars because if I have a base kit, the accent bars are beautiful, but I'd be worried about the board being too busy with the added visual interest of accent bars. But in a mono-colored configuration, the accent bars wouldn't be competing with the light grey alphas for visual interest.
From a practical standpoint, I don't think the existence of alt-alphas would impact the ability to hit MOQ since both the 40s kit and the base kit already include alphas.
For the alt alphas themselves, my preference would be to have weeb sublegends, but I know that's kind of divisive. I think hiragana or katakana would fit thematically since you already have some Japanese inspiration on the deskmats and the idea of a city train morning commute to school is a common motif in anime and Japanese media. Moreover, visually I think the extra "busyness" of sublegends would be welcome in the more visually simple mono-colored configuration. Lastly, I would want to include num-pad alphas in the alt alphas kit so numpad builds could get in on the mono-colored colorway as well.