Reading Analog Input Mesa 6i25 ( Potentiometer/NTC/PTC)

No.
Use an arduino to read the value and send to Mesa 6i25 as PWM or BCD code or even better as encoder velocity.

Sorry,
There are also some small DIP8 packaged chips that do voltage to frequency for 0-10V input, and output 0-10kHz roughly.
Very cheap and litle discrete components required.

Frequency is easy as all Mesa FPGA boards do encoder counting.
PWM, i never used so no idea how to go about it.
Plenty of us here use Mesa THCAD that reads the arc voltage from a plasma source and turns that into frequency that is read and displayed on screen again as voltage. We need this due to isolation from high voltage and interference.
Here are some of CNC plasma machines i have built:
forum.linuxcnc.org/show-your-stuff/38547...plasma-build?start=0

LM331 is very cheap voltage to frequency converter:
www.ti.com/lit/ds/snosbi2c/snosbi2c.pdf

What are you measuring? It is possible to bit-bang serial from some ICs including a thermocouple amplifier:
linuxcnc.org/docs/stable/html/man/man9/max31855.9.html
Though that needs 3 pins for the SPI interface.