Handl Defense is introducing a new SCAR Lower Receiver that takes standard SCAR parts without modification will accept Magpul PMAG's. The following photos are of a 3D Plastic Printed Prototype and not out of the 7075 Aluminum that the actual final product will be manufactured out of.

ETA: Also, the Handl Defense lower will accept standard AR-15 pistol grips, so your options have just become a little more increased with the versatility of this platform.