Wiring – How to Splice Multiple Wires In-Line

Finding a fuse with those characteristics is going to be difficult. I'd use a current shunt with a suitable MCU and circuit breaker and monitor the current taken by the device, shutting off the current if it rises above 120A for 15 seconds.

Two fuses in parallel can cause problems unless they are well-matched and the holders are properly designed. Any difference between them can cause one fuse to take more current than the other one, and fail.

This has been done, years ago, and not since. The reason was simple: It's easier, cheaper, faster, and more powerful to just use an FPGA for both the programmable interconnect as well as the programmable logic.

Of course, FPGA's are only good for digital logic. On the surface your approach seems to work for analog circuits, this isn't always the case. Analog switches/muxes/etc all have a non-zero resistance, not-insignificant noise, and limited current handling capability. This limits their usefulness to basic circuits only. For these circuits, it is much better to just wire it up directly.

In short, only people new to electronics would use such a device and they might outgrow it rather quickly. And it would be expensive.