Your idea changes the distribution of Gold Cup spots from the current 8 for North and Central America and 4 for Caribbean to 6 for each, and I think half is too many for the Caribbean. I doubt the Caribbean will have 30 teams that attempt Gold Cup qualifying. Looking at Wikipedia, 21 Caribbean teams attempted to qualify for Gold Cup 2009, 25 Caribbean teams attempted to qualify for Gold Cup 2007, and 26 Caribbean teams attempted to qualify for Gold Cup 2005.
If you are going to have qualifying, then you have to make it at least somewhat meaningful. 2 groups of 5 where the top 4 qualify is too much. As it is, 3 (or 3.5 for a 16 team tourney) is probably too much, but it's a necessary evil in the region where the N/C region is so much stronger than the Caribbean one. Even without all 30 teams trying, you'd still have groups of 4 (and possibly a couple with 3) where only the top team qualifies (with 2nd to the playoffs in a 16 team tournament), so the games would be meaningful. Also, more spots may entice more teams to try qualifying.
A way to have 4 out of 5 N/C teams qualify but still give incentive to finish as high as possible would be to use the qualifying to determine seedings for the actual Gold Cup. For a Gold Cup with 8 N/C and 4 CFU teams, here is my idea where the letter refers to what group and the number refers to what seed you are in the Gold Cup with 1 being the best: A1: N/C Group Winner B1: N/C Group Winner C1: Best CFU qualifier A2: N/C Group second place B2: Second best CFU qualifier C2: N/C Group second place A3: Third best CFU qualifier B3: N/C Group third place C3: N/C Group third place A4: N/C Group fourth place B4: N/C Group fourth place C4: Fourth best CFU qualifer Another decision that would have to be made is whether the CFU groups would be all in one site like the current format or have each team play every other team once at home and once on the road. I would expect many CFU teams have never played in a group stage where you play each opponent twice.
I don't know if this would be enough of a carrot for the N/C teams, but it's not the worst idea I've ever heard.
But then again, Canada might improve to the point of actually making the next world cup because they played meaningful games in Central America.
You know, you're right. However I was thinking of posting something related to allowing an up and coming team like Puerto Rico a chance to play in UNCAF. I never understood how the Central American countries think that having one group of four and another of three is fair.Especially with Nicaragua and Belize getting better. I actually saw the last UNCAF tournament on TV. There were no blow outs to speak of as in past tournaments. So sorry but I have to disagree. I like the idea of a Canada entering the tournament. It gives them a chance to have their own camp cupcake a la U.S. and gives them meaningful games to play against the foes that have cause them fits in the past world cup qualifying. I see both sides benefiting because tv viewership in canada for soccer could rise and Central American teams get a chance to play against a team that plays a similar style to the US albeit not as strong but still competitive.