Seeking advice on the purchase of an old RME Fireface UFX I.

I need something for live performance, as I don't want to take an OSX laptop, with aggregate devices and an interface.

Here is the intended setup:

Fireface UFX
- USB to an iPad applying FX and mixing and master out.
- ADAT to a Digiface USB via ADAT

Digiface USB
- USB to NI Maschine+ sampler
- ADAT to Fireface UFX

Digiface USB
- USB to Akai MPC/Force sampler
- ADAT to Fireface UFX

My concern is that the Maschine+ currently only works without audio glitches with class compliant usb interfaces if the interface is set to slave, and the Akai MPC currently needs to be set to master (with the Akai MPC it previously could be a slave, but this depends on what firmware is being used, as this changes per release!)

A workable compromise is that I could use the x4 analogue outputs from one of the samplers, and the Digiface for the other and therefore only needing one DigiFace USB?

Does the old Fireface UFX I have any limitations that might cause issues in the above setup?