QT: No, just no. This would make the size of the application EXPLODE. Plus, since the QT people are incredibly unfriendly towards the use of a static library (yeah, it's doable, but boy is it painful to achieve!), we'd have to add an installer, which is the last thing we want to do with Rufus. We looked into QT, multiple time, and it's just not a good fit, especially as we're not cross platform and there is no reason why the executable size should become much larger than our current 1 MB (which we think is already large enough for a mere bootable driver creation utility).
You might as well ask us to use Electron here, which, actually, is a much more attractive solution than QT in terms of easing up the life of an application developer. After all, who cares if end-users have to download a 100MB file just to display "Hello World"?... 
With regards to ReactOS, I really REALLY appreciate the project (and I try to contribute where I can), but I have a couple issues with it:
1. They simply don't have enough developers. This is not DOS that you are creating a clone of here, so you need the support, and especially financial contribution of someone like Google (or, if they actually had the balls: Intel) to get somewhere. Without developer investment from a large multi-billion software company, I find it very hard to believe that the effort can succeed, because, currently, they can't even manage to play catch up with proper Windows XP compatibility. For the record, Rufus 2.18 isn't even usable on ReactOS at this stage, as ReactOS fails with the most basic thing we can ask of an OS: returning a list of devices...
2. If they actually wanted to make it more attractive for people to test ReactOS, they would spend some effort on making sure it can be run from an USB Flash Drive. This is actually the main reason I added ReactOS boot loader support in Rufus, as I was really hoping they were smart enough to realize that a Windows To Go capability from an XP-like ReactOS would become invaluable to people (just like the ability to quickly create a bootable FreeDOS USB drive can be a life saver). There are probably tons of Linux users who would like nothing better than have the ability to quickly run a Windows application from a bootable USB container, when they find that WINE is not working. Yet (unless I am very mistaken, as I have not tried that again lately), and as has been the case for over 5 years now, it just doesn't seem possible to boot ReactOS from an USB Flash Drive without producing a BSOD. So I really have to wonder: What is the point of creating an Open Source implementation of Windows if you can't even recognize that the first thing your users will want is the ability to boot it from USB? IMO, this is the number 1 feature that ReactOS should focus on if they want to both make the whole prospect of using that OS a lot more inviting, and have more people contributing. For the record, because I'd really like to help the project, I've been trying to find time to look into why ReactOS can't boot from USB, but this requires A LOT of investment development-wise, and I just haven't managed to justify allocating the 2 or 3 weeks full-time work that I figure would be needed to investigate that (See point #1).
All of the above means that I am currently not very hopeful for ReactOS to actually manage to get anywhere. Possibly, they might get "decent" XP and/or Vista emulation in 5 to 10 years, but IMO, it'll be way too late by then, and I really can't fathom why companies who have A LOT to gain from a non Microsoft-controlled Windows-like OS (<cough>Google<cough>, <COUGH>Intel</COUGH>) are not massively investing into making sure that ReactOS has the development staff a project of this magnitude requires.