That part isnt confirmed.
What was confirmed:
MC Fucks Illusion, gains no power.
Did the Illusion have the Sups illusion powers? Evidence points to no.
The way his power is explained is it grips onto the DNA of the "victim" and subsumes it once the right chemical is added to active it. If the illusion had no Sup DNA, it would make sense no power was taken.
We'd have to see how the Duplicate's power works, can her clones Duplicate too? If so, it would make sense he'd gain the power too if he got said clone off and came on/inside her.
If it does work like that, then yeah, game over, MC can just create a clone and have him go off collecting powers. The funny part is though, the clone would have the powers, not MC. Again, depending on how her duplication power works. If when they get re-absorbed that all memories/changes come too, then yeah, he'd gain the powers, if not, nope.