It would be excellent to enable using USB ports in an FX Loop device.
Example of loop device configuration:
FX Loop USB 1/2
FX Loop USB 3/4
Send USB 1/2
Return USB 1/2
This would enable putting an external, computer or mobile device in a chain so we could use any external effects.
Yes, there are latency considerations and concerns. DAWs support “external device” (Ableton and Cakewalk, Studio One all have this). They have a “measure latency” process and then offset all other latency to accommodate. That would be challenging to support in the QC. but you could have a “test latency” button and provide information about the results, allowing the user to decide.
But for an, iPad for example, sub 10msec latency is reasonable to use a effects app (e.g. another guitar app). For Windows and Mac, plug-in hosts would work great.
Yes, this can be done if the computer is the master and QC is “the loop” - but this doesn’t let me put a VST/Au between devices on the QC grid.