Hi,

maybe not the expected / desired answer, but I would not consider such a setup.
Don't worry in any way, I am telling you this with good intentions in mind!

Under Windows, the advantage is that there are very low-latency ASIO drivers, with which you can completely bypass the Windows audio system and access the recording interface directly. This gives you the best possible stability and, above all, the lowest possible latencies.

Additional advantages arise with RME through the very well written ASIO drivers, which enable really very low latencies and also through the device design that the USB communication is very efficient through the FPGA itself (which can be updated via firmware upgrades) and not through any 3rd party communication chip, which may be slow or buggy, but is not reprogrammable.

Since you apparently have an RME interface, you should use the really excellent RME ASIO drivers as the basis for a solid recording solution and not build such a (sorry) "crooked" setup.

Apart from that, it has nothing to do with Multi Channel WDM, such a solution would be built with ASIO4ALL, but that is neither supported nor recommended in case of problems, because it is simply an unfortunate setup. In doing so, you are negligently giving away all the advantages of a valid setup that can be supported by the manufacturer, as it should be.

The usual way is to get a RME recording interface and - if needed - to expand the number of analog Mic/line/inst channels through ADAT or MADI. There is one option to add multiple interfaces supported by this particular RME driver. Officially supported and tested are up to 3 RME devices. But it has also disadvantages, as you need multiple TotalMix FX instances and "any to any" routing works only inside of a TM FX instance / recording interface.
Workaround is here to connect those devices through ADAT, but then you dedicate those "precious" ADAT channels for this purpose to cross-connect devices.
Another thing is that you need clock synchronization between such devices.
Either by choosing word clock or by using digital ports like SPDIF, ADAT, MADI to distribute clock from one master.

If you would provide more information about your setup and your requirements (number of ports), one could consider what alternatives might exist for you.

Another good meant proposal to you is to use a traditional DAW product from one of the major players like e.g. Cubase where all important basic functions and things like delay compensation will work well. The latest version doesn't need the license stick anymore. You only need to connect to internet from time to time. But there are also other "well known" DAW products known to work well and who have a name in the market.