Just flying a kite here, but it strikes me that (even with 4 heads) the U1 could benefit from an AMS feeding one or more heads. I think the ability to add AMS would be the best of all worlds. I appreciate the connection port for an AMS probably hasn’t been built in, but would it be possible to adapt some other port?
Filament changes take time of course, but they could take place while another head is busy.