Ridiculous, and nonsensical. If you're going to use an external DAC, why would you be dicking around with an iPad in the first place? And what do you mean "without a dongle?" You have to plug the DAC into the USB-C port (assuming that Apple hasn't gimped this capability out of the port, as they are wont to do), making it... a dongle. And how are you going to power your iPad then if necessary? Or use external storage (if that happens to be allowed)?
And you still have the general file I/O hassle on iOS devices.
Instead of turning a tablet into an octopus of wires and external junk, you might as well just use a MacBook Air. Then you get proper I/O, a keyboard and trackpad, precise UIs, and can use all kinds of software and plug-ins.