A custom shield would be helpful for the typical user who isn't proficient with a soldering iron, particularly if it were populated.
Through holes with clearance for all 4 screw holes of the Leonardo would improve the mounting of the unit. The footprint should probably be at least as big as the Leonardo. If it overhangs on the JTAG side of the board the screw holes can be behind any terminal blocks. Total footprint would increase, but it is probably worth it.
Jumpers would select pull up, or series resistors and maybe filter caps.
A thermocouple board that didn't interfere with the ADC would add 4 more analog inputs (perhaps a latch for the mux or even better, an I2C thermocouple/mux like Linear's LTC2495CUHF#PBF). The Linear part provides real differential input which would improve noise immunity.
An ammeter feature will be desired by some, TI's INA170 High Side Current Shunt Monitor is probably a good part to implement this.
A Yún friendly shield would have to be able to jumper out VIN from voltage monitoring. It might be nice if it supported an onboard power module to replace the Yún's lack of one (if not cost prohibitive, not typically populated in any case). Note - Yún and Leonardo shields may cause damage if plugged into the wrong type of Arduino.
Need to figure out level of interest to figure out method of assembly. A stencil and solder paste for the surface mounts and hand soldering the through holes would probably suffice up to 100/year. Should price out board houses as well.
A custom shield would be helpful for the typical user who isn't proficient with a soldering iron, particularly if it were populated.
Through holes with clearance for all 4 screw holes of the Leonardo would improve the mounting of the unit. The footprint should probably be at least as big as the Leonardo. If it overhangs on the JTAG side of the board the screw holes can be behind any terminal blocks. Total footprint would increase, but it is probably worth it.
Jumpers would select pull up, or series resistors and maybe filter caps.
A thermocouple board that didn't interfere with the ADC would add 4 more analog inputs (perhaps a latch for the mux or even better, an I2C thermocouple/mux like Linear's LTC2495CUHF#PBF). The Linear part provides real differential input which would improve noise immunity.
An ammeter feature will be desired by some, TI's INA170 High Side Current Shunt Monitor is probably a good part to implement this.
A Yún friendly shield would have to be able to jumper out VIN from voltage monitoring. It might be nice if it supported an onboard power module to replace the Yún's lack of one (if not cost prohibitive, not typically populated in any case). Note - Yún and Leonardo shields may cause damage if plugged into the wrong type of Arduino.
Need to figure out level of interest to figure out method of assembly. A stencil and solder paste for the surface mounts and hand soldering the through holes would probably suffice up to 100/year. Should price out board houses as well.