that had to be Japan
But can you see that if 64 didnt have the type of stun it had, that the combo game would suffer tremendously? I think they had a great hitstun balance, the problem was that the defense system was weak.
Here's the thing though, what separates Brawl from 64 isn't just hitstun, it's the fastfall. In Smash 64, the fastfalling is incredibly fast where as in Brawl it's extremely slow and has a slight delay after you've done a shorthop (i.e: I short hop and for like one second I swear I can't fastfall as early as I'd like to) thus 64 gains more combo potential because you can get to the ground faster and follow where your opponent DIs. Also, almost EVERY move in the put you in the tumble, why even Pika's Utilt at such low percents (I believe at 20% or even 30%) put you into a tumble. Where as all the moves in Brawl that are similar to that are weak hits and therefore don't juggle like they did in 64 and Melee.
Then there's the throwing and no wall techs. The great part about 64 was the fact that you could combo off of walls and walls were HUGE set ups for combos on certain stages. Throwing was ridiculous. Of course this is all common knowledge I'm mentioning you probably already know.
The BEST option I can think of after we have the hitstun code with about the same length as 64's is to make weak hits put you into the tumble. They don't put you into the tumble into later percents if I'm not mistaken, so, if we (in this case PW

) could somehow make it so weak hits put you into the tumble THEN we would have more combos than what we would have without it. They put weak hit attacks in there probably for people who DID want combos and could use them as set ups, as we've seen with the Brawl meta game this is true, a LOT of the weak hit attacks are used for set ups (i.e Fox's dash attack into Utilt or Pika's Utilt). If the weak hits were made to put you into the tumble, then DDD couldn't CG and neither could Falco (if I'm right his Dthrow is a weak hit too, correct?) Then and only then would you have Smash 64 hitstun completely. Smash 64s hitstun doesn't work well without these two factors.
1) Faster fastfalls
2) Weak hits putting you into the tumble at lower percents
Then I believe you would achieve what you're thinking of. Then again, I think that Smash 64 hitstun is a bit too much for Brawl but, for experimental purposes, I do NOT mind pursuing this idea if the changed hitstun code (when it comes out) doesn't help at all.
Edit: OR alternatively, like Magus420 proposed, DI weak hits.