Hello,
To add - if You are greatly worried about Your customers doing all sort of silly things, then You can use LACP passive.
With LACP passive, on EX switches, the LAG won't come up and won't process incoming frames unless customer correctly configured LACP on their side.
LACP passive also helps against looping of LACP PDUs. I.e. if You have 2 LAGs with LACP active towards same customer, and customer manages to loop LACP PDUs around, then the LAG loop will form. WIth LACP passive, this does not happen.
HTH
Thx
Alex