Have you tried Buddabing's ListGen utility? This is the sort of thing it was built for..
Anyway, I ran the listgen utility against a .92 version of MAME and came up with 193 roms that are not clones and are categorized by catver as 'Unplayable'.
select romname
from gamedata
where isclone=0
and catver_category like '%Unplayable%'
;
...Which, of course, doesn't match your 600 so I wonder where the discrepancy is? Where di you come up with your figure?
Okay, so using ListGen, I came up with 8 roms out of that 200 that are parents that are
not playable and have a clone that
are playable:
vr
jchan
bcstry
senkyu
titlef
wwally
landbrk
zeroteam
Here's the simple SQL I used:
select cloneof
from gamedata
where isclone=1
and catver_category <> 'Unplayable'
intersect
select romname
from gamedata
where isclone=0
and catver_category like '%Unplayable%'
;
I know this isn't exactly what you're looking for, but it'll get you 80% there and my gf's standing over my shoulder giving me the "evil eye" since I'm supposed to be getting dressed to go out

If you can't figure it out by the time I get back I'll see what I can do to get you 100% of the way there.
-Steve