R. Lowe's patches to support > 512MB RAM, larger hard disks, even what seems to be newer WDM drivers: https://www.rloewelectronics.com/
The KernelEx project to support applications targeting later versions of Windows: http://kernelex.sourceforge.net/
There are also fascinating articles penned by those involved in the Win9x development, like this one on the role of DOS in Windows 95, https://devblogs.microsoft.com/oldnewthing/?p=24063 that dispel the notion that it simply 'ran on top of DOS', it instead seems that Windows 9x was rather a vast expansion of the DOS kernel.
Given that Win 9x served as the introduction to computing for many of us, and that it has long surpassed any commercial benefit for Microsoft who now profit largely from Azure, wouldn't it be cool to have a peek behind the works? To see what could be hacked and extended combining these projects with the actual 9x codebase?
We've seen some generosity from Microsoft with the releases of the 3DMM, Console, and File Manager codebases. Building on this, wouldn't it be fun to play around with the old 9x sources and see where curious folks could take it? Not to mention the benefit it would have to older hardware and the retro enthusiast community.
And, with clear sight of the truth, perhaps we can dispel the notion that 'it's just DOS' once and for all? ;)