Well you've guessed it. Time for a Shiftry rant:
HP: 90
Well Base 90 is not that bad for a sweeper. But if you want it to be able to set up with Heat Rock (no Sash) it needs more Deence considering its next to awful typing. (Although EQ resistance is nice)
Def & SpDef: 60 ---> 85
Now it can set up Sunny Day or (if you have support) Swords Dance/Nasty Plot.
Spd: 80
If Chlorophyll is active, a neutral natured Shiftry wins over Swellow.
Atk: 100 ---> 120
SpAtk: 90 ---> 116
Now a potent mix sweeper on both sides. Shift also beats out its arch nemesis Cacturne's Base Attack stats by one point(SpAtk) and five points (Physical).
New Ability:
Intimidate.
Its a freakin' wad of Darkness wrapped in leaves, what's not to be scared about?
Solar Strength
Solar power is a little known move used by Tropius and the Sunkern Family, that raises SpAtk by 1.5 but decreases HP, in Sunlight. Solar Strength is a completely made up move which increases Atk similarly by 1.5, decreasing its HP.
New Attacks:
Well the new attacks are obvious, with its current boosts it needs better Physical Attacks (considering its Special movepool is quite fantastic). Its Physical STAB is limited to Razor Leaf, hence the induction of Leaf Blade and Night Slash to its movepool, double STAB and whatnot, as well as Sucker Punch, EQ and Stone Edge (since he learns Rock Slide already).
He could also be given the Elemental Punches and possibly Hypnosis to challenge Exeggutor in Ubers.
Well that's about what it will take to make the GREATEST Pokemon of all time even better.
Of course with Sand and Hail running about, Shiftry will probably stay BL, and usable in Ubers.
Nasty Plot one shot Solar Beam? CB Chlorophyll set? SD Sucker Punch and Leaf Blade's crit hax? Oh my!