And since DOS 6.22 and a boot a command prompt with Windows 98se is too similar, there's very little reason to do this. Do tell why?

Anyhow, the issues are simple. If you did install DOS 6.22, it would be on a FAT16 boot partition, then you might find PARTITION MAGIC with BOOT MAGIC to allow you to do this boot and combination.

I'd just boot to Windows 98se's command prompt and get it done.