I am thinking on replacing on of my members with primal regigigas and is currently thinking who to replace. I have a Mega Delta Gallade, Mega Delta Bisharp, Mega Eevee, Aggron, Primal Giratina and Zygarde. Who do i replace?
If I were you, I would not have three megas. You should just change one of the megas. Probably Eevee because Regigigas is also a normal type.
Is it for elite 4 rematch?
Yes and for post game as well.
There is also delta bisharp which dont worth a mega i think.
It is not bad, but for a mega, you can find better.
Just my opinion though.
I would suggest to switch Aggron. He feel a bit out of place, mainly because of its typing. Steel/Rock have many very bad double weaknesses (mainelly ground) that is awefull for the game. Even whit a Rock Head + Head Smash set, he is still weaker that Regigigigigigigigigigigas in terms of overall damage output. Also, Regigigas brings more speed to your team, which is always welcome.
It would look like this: