Olimar with 3 pikmin that last a lot longer sounds much better than 4 Pikmin, whether they last longer or not.
Stance Change down B, keep the current Pikmin for each attack except for Side B, give him a new F-smash where he swings the Pikmin currently active like a bat. Up-B can either grapple if the three pikmin are in range, or, if they aren't, he throws them upward, and holding up makes him propel himself along the pikmin chain for an actual recovery, after which the only action he can do is try to up-B tether again. Up-B'ing after he has already used the up-B chain jump acts identically to vBrawl tether and can not boost his recovery further. Make Pikmin more differentiated and less homogenised than in vBrawl. To contrast the fact that his pikmin don't shuffle out after being used, the Pikmin act very differently in terms of bkb, kbg, angle, shield damage, damage, and hitlag. Down B stance change is nearly instantaneous, probably at most 5 frames, at most, again, and switches to the next pikmin in his line. Side-B toss is also more differentiated, with some Pikmin causing knockback, some attaching, and some doing both. I have a list elaborating which do which ready if anyone wants to see it. These four factors- Different pikmin effects, more differentiated side-B, significantly less Pikmin to spam, and non-changing pikmin, would make his build something of an actual character, and make the Olimar player consciously think about what Pikmin he has in hand, knowing that he can't readily call back Pikmin with down B if he tossed out the wrong one, and make the player forced to use attacks quickly and smartly, as with every other character in the game.
Oh and Pikmin pluck would be slowed down considerably, something like, 30 frames, so you can't just throw your pikmin out and expect to refresh with new ones instantly.