Just like in real life, there will always be plenty of people who deviate from their people's customs and social norms.
All you really need to consider is:
A. Have it make sense for your character(s)--since you've already established your character as a rebel, that seems to be covered
B. Realize other characters may find it strange IC (though given the amount of people already playing monogamous Miqo'te in game, perhaps they won't)
C. Be aware their tribe(s) will likely exile them. I don't think most tribal Miqo'te would take kindly to one of their own marrying into a monogamous life.
All you really need to consider is:
A. Have it make sense for your character(s)--since you've already established your character as a rebel, that seems to be covered
B. Realize other characters may find it strange IC (though given the amount of people already playing monogamous Miqo'te in game, perhaps they won't)
C. Be aware their tribe(s) will likely exile them. I don't think most tribal Miqo'te would take kindly to one of their own marrying into a monogamous life.