To me ideal is like Morde and Rumble...
I was thinking like Singed. AP Scaling but builds tanky (Rod, Frozen Heart, etc.) rather than an AP that can deal damage primarily but take a hit secondary. Her Q is decent damage (230 +8% Current/Missing Health, +2% AP) and on a short cooldown so no AP is still decent sustained output.
Edit: I suppose I should say AP Tank instead? Dunno. Regardless, she doesn't NEED AP for her Q's to be effective so she's free to build more tank items.
I don't feel like Elise is bringing that right now, and it's why I don't and can't see her being run as an AP mid. Her scaling is frankly awful when you look at the whole picture, so why build in that direction at all?
I agree that she probably shouldn't be run as a mid. Her W is her best scaling skill and it's unreliable as a damage dealer barring Spider -> Human -> Spider situations ... that you wouldn't want to do as a squishy AP Mid. Her Q is more a harassment tool rather than a burst caster tool.
My issue with her so far is I'm not entirely sold on what she does in team fights. Spiderlings melt to AoE damage, even with their 40% DR, and her W Heal needs either better scaling or needs to get better with points in W (right now, 4 + 2% AP flat; I'd even be fine with 4/5/6/7/8 +1% AP, honestly).
Also, her E needs something passive to it
![Frown :( :(](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)