I dont see why you couldnt replace the board with the only exception/problem being the touch screen they use is not a standard touch screen and they are running custom code to make it work with the Marlin firmware (I heard “rumor” of marlin firmware developers attempting to backwards engineer the touch screen to make it compatible but dont have much on this) so you may not be able to get the screen to work and will have to rely on network based or usb connected printing.
I believe you can request to be sent the source code of the firmware, this is hit or miss as I know they have done it on other models of their 3d printers not sure about this one.
EDIT: Looks like the source code for the latest firmware release is listed under their downloads section for the SV04. Firmware Download | Sovol3d
I am just now diving into trying to use OctoPrint with this printer, I had it running with the SV02 so I imagine it should be possible to have it work on the SV04 but I literally just started configuring it this morning and Im currently running a print off the sd card in the printer that still has a couple days left to print so I wont be trying it out anytime soon to verify.
I too would like to know about the use of Klipper, I want to say given the creality board that is being used it is possible but again the touch screen may become non-functional so you may have to come up with a different solution like klipper screen.
I hope these answer help even if its just a little. So far after getting this printer dialed in, I have been absolutely loving the results. Oh I am using a Creality Ultrabase glass bed and it is amazing and eliminates any worries of an uneven build plate, just bump up the bed temps to 70c for PLA and you are golden.