I've been keeping notes on something like that, and the best direction to take would be to make a different version of the NT mod that takes advantage of the natural strengths of that version. For a start, it'd be a lot more insular so I wouldn't have to worry about compatibility with other mods, so that could translate to all the .exe hacks that are at present only in beta for the PC version of NT; I'd also have up to 9 discs to work with which can each store their own set of files. This could be used for a lot of different purposes, such as branching the story, different party leaders (9 characters, 9 discs
), scaling difficulty in NG runs like Dark Souls, etc.
There's also some cool tricks I've seen where enemies can be made into controllable party members. I don't know the particulars on that, but there's some interesting possibilities there too. As far as the mod's gameplay goes, I'd likely make a pared down version of NT for it. A lot of the new enemies would be either omitted or scaled down in some way; it depends on the space constraints in the scene + kernel (assuming they're more stringent than the PC ones). That's the biggest limitation of the PS1 files; they can't be too large, and player/enemy models aren't easily altered (the PS1 modders have to do it by Hex, rather than tools like Kimera; props to them, I say).
But then limitations have a way of focusing your attention better, so it could work out into something worthwhile. Once I've got the mod settled here, I'll start making moves toward a re-geared PS1 version of NT...assuming I'm capable of actually doing it, of course; I've very little programming experience and no formal education in it.