Yes, but following this procedure we can't save users from the fraud.
but for your initial ethos:
One question that every time bothered me - how people can solely implement crypto in their life without any third-part intervention.
your "we" should not be involved
i answered your question of how the users can do it themselves
its not just a "mutual benefit" thing
but a "mutual destruction" thing
dont make a service where you want to be a police.. while advertising there are no police.
instead say "its the users own faults. its their funds they both cant agree on"
don't mother people. if they want independent control then they need to independently be responsible
P.S
if they both cant agree.. then the funds just dont move. its not technically lost. its just waiting for an agreement.
they just need to take time. have a coffee, cool off and renegotiate once cooled off.
if they cant. then take another break and then try again
its a case of just let them fight it out using their own hands found at the end of their own arms
but by using a 2-of-2 multisig both sides have an equal fighting chance. because both have fists and one sides hands are not tied