Alright then. Now that I have my hands on RD and the cutie mark crusaders...
The heads on these gals come off super easy but are a bit tough to put back on. You really have to mean it, so if you're going to paint a faceup, do it AFTER rerooting. The joy is that they only have a simple ball which will make customizing easier since there is less likelihood that the neck will break. The vinyl is much harder than a MH head, so I'm not sure if my needle will hold up to rerooting one. Might be safer to do hook and loop on these ladies.
Clothing that fits - since there are no fashion packs.. yet;
Lalaloopsy, some Bratz - though EQG are thinner and less busy, this is also true for MH clothes. I found that MH shoes with open parts, like Frankie's blue and yellow buckle heels work well ehough if you wiggle the foot in gently (EQG toes are wider), but since the angle of an EQG's foot is less pronounced, she won't be able to stand up without help.
Cutie mark crusaders fit in Kelly sized clothes. They might fit in some puki puki sized things. The thing to remember is that their legs are long. They look like they would fit in clothes and shoes made for 11cm obitsu dolls, but I haven't tried it yet.
Any others?