as it was said the lock is on apple's server side and there is not a resistor on the mother board which can help
, there are only two ways to use the ipad ;
1 bypass mdm which you do not like, i do not like it too
2 reprogram the nand with a valid sn wifi bt, and if it is a cellular one you must convert it to wifi and replace the wifi ic if needed, then restore it and you are done
i hope this is clear to you