a new breed of Catlist (it WILL be different!) ... (did I tell I started that Catlist from SCRATCH?)
Please tell me you are not going for a single category/subcategory per game. It makes much more sense to be able to specify multiple 'labels' for each game, e.g.: Street Fighter = 'Fighter' + 'Versus'. That way you can also define a single label 'mature', and not having to duplicate every category that contains a mature game. It also means that games that have driving and platform parts can be labelled as 'Driving' + 'Platform', instead of forcing them into a single category. You could also merge in the nplayers file as that would just be a represented by a bunch of additional labels, e.g.: xmen = 'Fighter' + 'Coop' + 'P4 Sim'.
The main challenge will be to decide upon the labels and how to keep their amount as small as possible. Oh, and all FE's will need to be changed as well 
You're taking the wrong approach at it, or at least a different one. I'm not looking to re-invent Catlist. Comparing it to Catlist might be a bit off, because while it serves the same purpose, I wrote with my personal priorities in mind and will serve as such (Those being to "work for me" for my Cabinet, while not losing the incredible amount of information and artwork in the process,a dn to display properly in QMC because I'm working on a mac and so is my cabinet). Ok damnit, I had planned not to talk about this until it was finished, but since I sprang my mouth already (and honestly thought no-one would dive on THAT part of the post)
- All Games are in there (up to 0.148).
- Parents & Noteworthy Clones will be sorted as in catlist, only with significantly (!!) less categories (we're talking *only* 78. for instance I really don't care about my point-of-view in a race-game. (Which is not a good example because all games that you race car-like vehicles are sorted in either Racing / Circuits or Racing / Touring, which means going in circles or from A to B).
Note that these will mostly suit my english-speaking needs (except for where history.dat says it's worth it to include the mostly Japanese one as well (yes, I read most of history.dat to figure that all out). Games that only appeared in Japan or such are in there as treated normal.
- Clones that didn't make that cut, but have different flyers as their parent counterparts are stored in a seperate tag -> ZZ - Flyerclones
- In recent efforts to clean up history.dat there's a lot of cases where the parent's entry would just say: export Version, look at the japanese one! separate tag > ZZ - Infoclones
- Only working games in the Main list. Preliminary drivers are stored in ZZZ - Preliminary.
- The ones that didn't make all that are stored in ZZZ - Clonebin, hoping to make it out someday based on new history.dat information. Let's Pray for them.
- Gambling games Is the only thing I did quite selective, If I liked what I saw i put it into Gambling, If I didn't I put it in a folder called ZZZ - Unspeakables. There's really no need to be there.
- The Mature Issue has been broken down into 6 categories (with Mature as first prefix, so it would stay together).
- The [Veradded] "column" is not used for tracking which MAME it was released in, but it displays the Hardware System it was Built on (like CPS, Arcadia, NeoGeo, PC-10 etc.)
- Some other stuff/ideas for dividing the Clonebin to get it in compliance with history.dat, but that's not for now, might not even be for release.
As said I'm not reinventing anything, I just put a HUGE amount of manual labour to build something into something the way I wanted it to be.

(reading history.dat, checking all flyers and playing next to every game to be able what mattered for me in the sorting of categories and keeping those numbers a bit lower.)
Anyway... On-topic?
