Whelp, trying to run the installer and VN itself on ReactOS gives the same errors as one gets on XP.
This isn't exactly surprising as ReactOS is specifically targeting XP compatibility and even identifies itself as NT5.2 (same as XP x64 and Server 2003; for reference Vista is NT6.0), but this does mean that it, like XP, will too be completely out of the question in terms of being compatible with the "ultimate edition".
I mean, it kind of makes sense since there is a lot of software and hardware that's basically stuck with only supporting XP at the newest, so attempting to make a FreeDos equivalent for XP can be particularly useful, especially since compatibility between Vista and even Win10 hasn't radically changed unlike the XP to Vista transition (even more-so considering the incompatibility between 32bit drivers on 64bit OSes).