Dipping into the pyro costs the following: Autohypnosis 5 ranks, Craft (alchemy) 1 rank, Knowledge (psionics) 2 ranks, 2 skill points, 1 BAB, 1 HP, slower weapon enhancements and blade skills, can't power attack touch attacks.
Which grants the following: Ability to use a single 1d8 fire damage only touch attack at 15ft, manipulate existing fires.
Right now you can throw a light 1d6 mind blade 20ft with no penalty. Making it a 15ft whip would let you add things like tripping, cleaving, and whatever abilities which you can't do ranged, which is what you'll be wanting to do otherwise you'd just throw your mind blade (mechanically, I know the aesthetics are cool but we're doing mechanics). Now personally I would allow a 1d8 two handed weapon with reach off the bat because it's a reasonable trade off (and with mind daggers I guess you could threaten 5ft away too). Now if you're tripping and cleaving then you're already spending those feats, and I hate the idea of making melee spend lots of feats to be a one trick pony. So what I would do is let a blade skill give you a whip form. The damage would be somewhere around 1d4-1d8, depending on my mood. 1d8 may outshine the pyro's whip just by being so much cheaper to acquire, with the only difference being it's not a touch attack and it doesn't do fire damage. 1d6 is probably good.
tl;dr I'd allow a 1d6 15ft whip form (no touch) if you spent a blade skill on it.