>>96311825
You should ask your opponent's approval to use any variant or design that is not featured in the MUL specifically under your faction's listing for the given time period. If you are unsure or confused as to whether or not a mech would be appropriate for play in a specific case, you should communicate with your opponent prior to game-time to prevent unpleasant surprises.

I am not sure why you are still confused on this matter. You don't need my approval for any mechs on your list as long as your opponent is cool with what you're doing. An opponent similarly does not need to justify on any grounds why they won't play with you and your list. It is in your best interest to choose mechs that fit the agreed scenario in nominally standard formations.