Unfortunately you cannot use a Waves card in the ME-U as Waves SoundGrid does not transport clock data at present. Me-U can take Dante, EtherSound, MADI, and of course ACE/dSNAKE & Aviom.
As you say, you can fit an ACE card in the iDR and a Waves card in an xDR-16 (which would be limited to 48in 64out). Then use Link 2 on the ACE card to connect ME-1.
This is because 16 of the 64 inputs available from the Master Port B ACE card are used up by the 16 analogue inputs on the xDR-16, leaving 48 that can be taken from the xDR-16 Port B. On the outputs side, the same signal can go to multiple outputs, so the 64 Master Port B ACE outputs are all sent to the xDR-16 Port B slot. Eight of these 64 will overlap with the 8 XLR outputs on the xDR-16.