Each release to the public (us) requires a day or two to create a system to deliver the code to us. (assembly, testing it, etc). Paradox decided last year that they did not want to have a lot of smaller patches due to the amount of time it would take away from 1.4. In addition the modding community would go nuts with 1.3a, 1.36, etc. imho having just one patch is much better than many smaller one.
I can see the reasoning, but I think it's a balancing act between current version's playability and the benefits of having less patches.
If 1.3 did not suffer from few of more serious bugs that it is suffering at the moment, I would agree that it would be smarter to save that 2 or 3 days just to get the big patch rolling out (given the size of PI programming team, which makes every (wo)manhour of programming even more valuable compared to larger corporations). But I do not think that 1.3 is in a state to be left alone for this long of a duration (5 months for a beta).
And I wasn't really proposing 5 different patches, I was really asking just for 1 or at most, 2 hotfixes to fix major bugs (like AI superstack) while we wait couple months for whole batch of smaller stuff. I doubt such patches would guarantee breaking compatibility, and even if it did, then it's up to the mod users and modders to make their mods compatible to every single hotfix; they are not forced to. If they wanted to, they can still just use the compatible patch version and wait out for the big patch, while smaller hotfixes would give options to those who play vanilla something to go by while waiting months for any sort of fix.