Don't undersell yourself.
Do yourself and your friends a favor and get paid what you're worth, whether that means more equity and/or more responsibility. If you're worried about the fallout from your friends, as if your friends would shun you for pursuing your worth, check your premises.
What's this bull about everyone being replaceable? That sounds like something your "money holder" would say to try to keep your equity stake low. I left my last company because I didn't feel that I was being paid fairly in equity. It's an unfair and unfortunate situation to be in, but it's really your responsibility to shape up and demand what you deserve.
Good engineers make themselves replaceable by writing legible code. This sort of 'replaceability' is invaluable, and should lead to higher equity if anything.