Forest and Southampton reached the semi finals last season. Southampton even beat City.
If they put it as a priority, Brentford and Villa could go beyond that. They could easily beat a slightly weakened United/ City/ Arsenal/ Liverpool etc side on their day.
You could even apply the wider logic to Arsenal. They have won only five major trophies (all FA Cups) in the last 20 seasons. Why on earth aren't they going for it? For the sake of a few extra games, it could give the club a huge lift. Quite interesting that before United's biggest spells of dominance, (93 - 2001) and (2006 - 2013) we won the League Cup in the season before.
And ultimately, this is the issue. An expanded Club World Cup isn't going to go down well once its started and gains a regular spot in the calendar.
Forest's draw = Grimsby, Spurs, Blackburn, Wolves,
United
Soton's draw = Cambridge, Weds, Lincoln, City,
Newcastle.
Soton beating City is the only result here that would really raise eyebrows, Forest beat a poor Spurs team I guess but issue is the top 4-5 teams operate n a different playing field to everyone else (and within that you now have 2, maybe soon 3 countries owning football clubs). If you get to a semi or a final as a mid table team, the big teams won't rotate (like City did when they lost to Soton) and you'll face their full strength team and 99 times out of 100 lose. It's basically a top 4 comp dressed up as a domestic cup (the non European qualifying PL teams even have to play more games!). Look at the winners past 10 years (City, Chelsea, City, United, City, City, City, City, Pool, United) versus the 10 before (Boro, Chelsea, United, Chelsea, Spurs, United, United, Birmingham, Pool, Swansea) and if you keep going back it's competitive. It just isn't now and hasn't been for a while.
Arsenal went for the FA cup under Wenger because they didn't have the money to compete for the PL with the stadium debt +it was the only realistic trophy of significance. They were also unlucky in the CL (Pep's Barca dodgey red & Lehmann madness versus Rikjaard's Barca in the final).