One of the biggest things I've had issues with has been the faulds across the abdomen, and the pelvis.
I have a strong martial arts background (my main focus was CLFBS and Northern Shaolin kung fu), so my other MA buddies and I usually show off a fair bit at events in our body armour. Being a panther and dragon stylist, there is a lot of twisting and bending involved in my styles, and armour can be very restrictive.
To get around it, I ended up breaking my armour into many little overlapping pieces; a scale armour instead of solid plating. This can be a lot heavier and a hassle to get on and off, but it gave me the flexibility and maneuverability I needed.