Huge Playmobil fans here too (my dd is 6 now)! I wouldn't mind the jumbling up but encourage it if that is what gets her playing with it :-). My dd tends to enjoy Playmobil in quite random combinations, whereas sets set out as they were intended don't seem to grab her imagination in the same way.
Anyway, my suggestions for a 5yo would be:
Magnatiles. They are expensive but great fun and have been our best toy investment ever, we first got them when DD was 3 and her older brother was 6 and they have been played with if not daily then at least several times a week. We started off with 100 as a joint gift to both kids and have since added to the collection every year. They are mainly used with the Playmobil or other figures to build castles, zoos, prisons, mazes etc. When other children visit they always gravitate towards them, whether they are 2yo or 10yo.
Play silks - despite access to other dress-up stuff, play silks in various colours are what my dd and her friends use the most for dressing up, but they are also used with the Playmobil as grass, sea or sand, as bedding for dolls, as fishing ropes, horse reins etc etc. Also quite expensive but used for years and very imaginatively.
Board games - we love the Gamewright card games! Sleeping Queens has been a hit with any 5yo we have introduced it to (the box says from 8yo but perfectly fine for a 5yo). Otherwise Rat a Tat Cat is great fun too, not to mention Duck Duck Bruce (if you can find it).
Oh, and for Lego, I would probably start with a small set that is easy to build, to see if she enjoys following instructions, along with a box of mixed bricks without instructions, to see whether she prefers to build her own creations.