According to Barney there's 348 pages of Mean Arena so I think that's going to have to be 2 volumes.
Similarly there's 321 pages of Finn so that'll either be an incomplete run or 2 books (only the first 2 books were reprinted in the floppies implying it's diminishing returns from there but that's only 120 pages so a bit slim).
There might be enough space to squeeze all the remaining ABCs plus Robusters in 2 volumes:
Vol 7 - Return to Earth/Mars/Ro-busters = 74+79+83 = 236
Vol 8 - Fallout + Robusters (orient express/terra-meks/ro-jaws and hammerstein) = 86+12+27+78 = 203
Could potentially swap Return to Robusters and Ro-Jaws and Hammerstein over to split the Ro-busters material over the 2 books.
Following Indigo Primes advice I've split the list up.
Things that were mentioned by name (11-16 books):1-2 Finn
1-3 Sinister Dexter
1-2 Strontium Dogs / Durham Red
2-3 ABC Warriors/Robusters
2 Brass Sun
1 Blackhawk
2 Mean Arena
1 Revere/Cradlegrave (possibly also Slaughterbowl as it's recently had a digital release and would just fit)
Speculation based on spine spine art (5):1 Blunt
1 War Machine/Fr1day
1 Sam Slade
1 Devlin Waugh (post Smith)
1 Leviathan (plus some combination of Helium/Detonator X/Interceptor/American Gothic/Stone Island)
My speculative list (8-12):1 Survival Geeks
1 Armoured Gideon
1 Flesh (Midnight Cowboys, Badlanders, Gorehead)
1-2 Dredd
1 Stickleback
1-2 Deadworld
0 or 2 Zenith (it's the biggest name strip we've not had but I'm not convinced it'll appear)
1 Tharg's 3rillers (Mechastopheles, Infestinauts + some others)
1 Scarlet Traces (you've convinced me this is possible and Scarlet Traces-Home Front is 247 pages of strip which is a thick book but we've had bigger)
Total = 24-33
Things I'd really like to see but suspect we won't get:Kingdom - with only 2 stories left there's just not enough for a book
Savage -
FB page replied to say no plans for more savage in the collection
Peter Milligan collection including The Dead
Defoe - one story short of a full run which is a shame
Tor Cyan -
FB page replied to say no plans for more
Things I don't think we'll get because they don't fit nicely into the format:Harlem Heroes - the stories just don't fit nicely into ~180-200 page volumes and we're already getting future sports in the form of Mean Arena
Luke Kirby - it's just slightly too long for all of it in 1 book
Things I'd really prefer not to seeSkip Tracer - no one needs this in hardcover
M.A.C.H 1 - it'd need 2 books and having read some digitally it's really not aged well
Bec & Krawl - got digital in the Humble Bundle and it's a bit meh