You most likely trolling anyway but there you go;
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"The stronger my opponent, the stronger i become myself. I never tire and never fail"
On a more serious note, no kisame wouldnt pose much of threat for either ems madara or edo madara. If edo madar was to summon a meteor that is kisame done i dont believe he can regenerate from that because in order to regenerate he has to be still alive and i dont believe he would be after the meteor.
Secondly kisame has a 2.5/5 for genjutsu and thats basically the same stat as naruto who has been trolled enough by genjutsu. What im saying is that genjutsu is kisame's weakness and onces madara either edo mor ems does what he did to A with a sharingan genjutsu that is kisame there for the taking.
However being partnered with an uchiha illusionist and even telling deidora that he lost the moment he looked into itachi's eyes, kisame obviously wouldnt fight an uchiha whilst looking in their eyes. Kisame is one of the few people who can counter madara's extreme katon jutsu's with his own suiton techniques. If he fuses with samahada he will prolong the inevitable which is his defeat either to ems madara or edo madara