> would be possible run MorphOS (EFIKA version) on MPC512X ARIA board

No, because the Efika 5200B and the ARIA board are too different, down to the SoC and even core levels.

> what needs to be changed to make it possible.

The MorphOS team would have to port MorphOS to and write drivers for the ARIA board, which would include the MPC5121e/MPC5123 SoC (e300c4 core + uncore (+ PowerVR MBX Lite)) and the other on-board components.