Riot, if you really REALLY don't want Lulu to be anything but a support, here's what you do:
Step 1: Remove ALL DAMAGING AP scalings from her kit. Everything that scales with AP. Glitterlance, Pix, and help, pix damage are all JUST base values.
Step 2: Give her back the bases and values she had from before season four and the resulting nerf train she's been hit with. And while you're at it, give her back her AP boost on whimsy ally cast.
Step 3: balance her from there if she's still underpowered. Mid/Top lulus will never be able to scale at all in the late game, damage wise, and support Lulus will build her as they've always built her: For utility. A Mikaels/Locket/Censer build doesn't care at all what her AP ratios are, and in fact, neither does ANY support. AP is a dead stat on real supports, I mean, look at Soraka's scaling, she gets what, 30 damage out of a deathcap? AP utility scaling was just asking for this kind of "anti-fun" mid play and all its done is cause nerfs and worthlessness to any champ who got them. Janna's horrible? Too bad, she'd be anti-fun mid with her utility scaling so we can't buff her. Lulu's in a great spot support? Too bad, utility scaling makes her a lane bully anywhere else, have a half dozen nerfs. Soraka's playable? Pfffff, get olafed again while we take five patches to decide how to lovetap Lee Sin. Sona now magically needs a full rework. Taric gets dumpstered because he was broken with an item. Even frickin' Nami is getting nerfed, despite being the ONLY traditional support champion who ever gets any competitive play and even then in maybe 1/12 games when Braum, Thresh, Leona and whatever mage is FoTM is banned.
Tl;DR: Delete scalings. Give us back our base values. Boom, Lulu is a support only again.