Should you be able to add more the one polarity with one forma to lessen the grind??

[Kusungphak]

I think I forma'ed only a single weapon and that for an achievement. I need those formas to build new weapons for now. 

But regarding OP's suggestion it really wouldn't bother me as it doesn't diminish any value. But I don't think its going to happen as forma can be bought from the market and I am pretty sure its a commonly bought item. Slim chance this is going to happen. 

Oh regarding the Mastery argument few posts before. Mastery means nothing. People should play how they want to play. I like to play for Mastery but if someone wants to level up to 14 and continue its their style of play.