Nobody perceives ReactOS as a threat at the moment, but I wonder what Microsoft's stance would be if the project developed much faster, for example by receiving funding from a bigger institution...
Cut Windows licensing charges for corporates to ensure that the total cost of ownership of Windows is lower than ReactOS. IMHO ReactOS should target corporates who have old Win32 apps still running on XP or Win7 that they can't or won't migrate to Win10.
There should be a ReactOS crack team out there, helping people with such things. I have seen in the corporate world, virtual machines running Windows XP, carefully hidden from the watchful eye of the Nazgul, I mean corporate IT. Why? Some function or other can not run in newer versions of Windows.
However, such a ReactOS installation would hardly be blessed by IT either... not anymore than a random Linux installation. :-/
Where I think ReactOS could shine is in the embedded realm. In that realm, you often have custom development anyway. 100% compatibility is often not needed. You might have product initially done on Windows Win32, then tweaked to run on Windows CE (or whatever they call it nowadays). Instead you could tweak it to run on ReactOS and call it day. Since ReactOS can take standard Windows drivers, getting BSP support should be feasible.
Also, ReactOS should offer EC2 images like Ubuntu does:
I've seen that too - but with corporate IT dept support - at a large UK mortgage lender running a loan origination system initially built in the 90s with an MFC Win32 GUI. Over the years the system has been so heavily customised by the vendor that it's practically bespoke. Migrating the existing system to run on modern OSes, or adopting a new system would be a huge expense, and can't be justified by any rational cost benefit analysis. IMHO there's a huge overhang of legacy Win32 GUIs out there. I'm hoping they'll fund my retirement.
I don't think it's possible for ReactOS to target corporates anytime soon with the current device driver database - Linux + WINE will do much better at the moment.