If there were any merno sprites (I can't find any) I would have him fight fleetway and there would be 3 parts the first part would be merno after beating destroyer vegeta and True MUI goku fleetway would encounter him and sense his enormous power level (And know he is a clone since he has encountered clones before) and fleetway would power down to base ssj4 to talk to him and merno being impressed with his power and knowing he's hiding a lot would offer him to be a destroyer in his new multiverse Fleetway would then tell the clone a few things about goku and vegeta and how he even though he's a clone he would give him tips on how to be more efficient and then he would give him one last tip and say you should never trust anyone ever (Reference to the ToP) And he would skyrocket his power and hit merno with an energy blast big enough to incinerate him instantly fleetway would then be filled in on what has been happening in the dbz universes and would then try to track down the original merno after fleetway would become dangerously close to finding the original merno a merno clone would be sent after him except this time the clone would be prepared and enraged for last time fleetway would then fight the merno clone at Full power with ssj4 but would be beaten and outclassed in the fight and forced into ssjg and he would start fighting him a lot more vigorously but would still be extremely out classed and be forced into ssjb knowing that mernos clone is still holding back a lot power so he would create a bunch of clones to buy him 5 mins while he created a spirit bomb to get rid of the clone for good and he would then use its energy to create a giant explosion causing merno to go ultra instinct and then he would beat fleetway until he reverted back to base form but just before he would be killed by merno he would jump through one of his portals right before it closes to vampa and would be found by broly and broly would give him some of his ki to help him stay alive and After a While (Fleetway is at 100% again) he would think about his next move but then goku and universe 9 angel and god of destruction would instant transmission to planet vampa and they would then explain to fleetway/broly that the original merno has been merging all his clones together and that they need both fleetway and broly to learn MUI and to help protect universe 9 sense it has the weakest warriors they would agree and then learn mui and help protect universe 9 for when the original merno comes for it .

Just thought this was cool couldn't find any merno sprites so I settled for these

There in universe 9

And even though the one guys in super saiyan 2 merno has stated that LSSJ3 broly is only half as powerful as the saiyans from universe 13 so yeah he's strong