How do you want to perform analog mastering?
Do you intend to use an analog summing box?
If not, how many external effects do you have?
Do you plan to chain them analog?
Or do you want to connect each device individually to a recording interface to have the flexibility to use as insert in the DAW and create different mix buses inside the DAW?
No matter what you do in particular, I would base such a solution on an RME recording interface to have more flexibility in routing. What RME recording interface you use depends on how much flexibility you want to have in terms of analog i/o and possibilities to expand.
The ADI-2/4 Pro has predefined routings, but not the flexibility of TotalMix FX. It's a converter, not a recording interface.
IMHO, best is to get an RME recording interface as base and then - if you want - to integrate an ADI-2 Pro or ADI-2/4 Pro for the monitoring and to perform the final A/D conversion.
BR Ramses - UFX III, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1680v4, Win10Pro22H2, Cub13