ZDoom

as for the "god ray" effects, that should be mimicable by using png textures.

I'd certainly be there to help. And I am not too concerned with making it just like it was in Legacy. I'm all for improvements. Now I don't know much about the lighting in GZdoom. But I am pretty sure that it should be possible to get something that looks at the very least just as good as it did in Legacy. Most of the light effects used in Phobia is using the coronas to create visuals that GZDoom couldn't easily copy. And I figured that it should be possible to create similar coronas using scaled sprites in GZdoom if it doesn't have a Coronae system in place.

This is a mod I'd really like to get working but the amount of effort needed to get it done always felt overwhelming.

If someone else is willing to work on the visual side of this I would see that the scripting works as intended. As I see it, fixing the visuals is by far the bulk of work here, though because so much depends on Legacy's quirky lighting implementation.
I understand that you lack the time to help with actual work, but since it's your mod, if those working on it have questions, would you have time to answer those?

But be it as it may, I think the biggest roadblock here is the lack of a usable Doom Legacy version to use as a reference to compare against. I'll have to take a look if the one I compiled over 2 years ago myself (after excising some of the more broken code in it and eliminating some hard dependencies on GCC) is sufficient, but anyone interested should know that this thing can hardly be called stable (because there's no way to sugarcoat this - the code base is a total clusterfuck) and I really have no idea how it stacks up against the real thing from 15 years ago, but it should be enough for occasional comparisons.

I've been thinking about this for a few years now. 

Doom Legacy is all but dead and as I understand it unplayable for most people these days. I saw someone trying to play Phobia with GZDoom on youtube and it was (as expected) pretty much unplayable. 

Anyway, I was wondering if there's any interest in helping me convert the project over to use GZDoom instead. 

TBH I can't do it myself, I already cancelled one project that meant a lot to me because I dedicate pretty much all my resources and free time to DOOMBRINGER these days. Which is why I am throwing out a line here, to see if anyone would find the prospect interesting.