ok you have a strong arguments but we have to look at the Sikh Rehat Maryada. Is it not Man-made? From what I have read, a group of Sikh Scholars met (either in the early 18th or 19th century) to outline the Sikh Rehat Maryada. Is a code written by the Guru himself?
Reference:: Sikh Philosophy Network http://www.sikhphilosophy.net/sikh-sikhi-sikhism/5232-amrit-is-it-for-everyone.html

Furthermore, Guru Nank Dev Ji and every other Guru did not baptise themselves according to the way Guru Gobind Singh Ji described but I am pretty sure they achieved enlightenment too! So is it really fair to say that not choosing to take amrit is alright. I mean salvation is still attainable.
Reference:: Sikh Philosophy Network http://www.sikhphilosophy.net/showthread.php?t=5232

I am not supporting to the scholars who say it is wrong but I am just questioning the fact that 'moksha' or englightenment >>> is it still attainable without taking amrit?