What I did was got to 30 as a str melee, then only played as shifter from 30, held at lvl40 and redid Lolth over and over until I had enough XP to get 2 LL feats. Only when I got enough xp for that, then I went and did immo and played as humanoid (I got humanoid to LFF3 first). It takes surprisingly few runs to get this done.
It wasn't too rough, tbh, biggest rough spot was early LL when things suddenly jump up in difficulty (and you need the AC and AB to get around). Using Humanoid, Myco was an unbelievable pain in the butt at LFF1+2, but at LFF3 it as pretty much painless. Once you get to upper 50's is where this shines. Your main problem will be picking the most effective form: I've used Kenku, Lizard (mostly bosses), Risen, and Drow - so far all are very strong alternatives and can fill multiple roles.