My problem is not the form it's that where would you learn Vapaad being that it's a pretty advanced thing to just come up with on your own, FAD characters can come up with ways to learn the 6 forms currently presented and this could be said of Juyo but Vapaad is something that took a Jedi Master time to come up with the idea and implement it. If the canon says Mace leaves something on Vapaad behind then I will have no qualms with its inclusion.
However my problem with Juyo is that we have 6 forms 6 classes and being that FFG has done things in a way that suggests they like patterns, I know there is only one form left but I don't see them adding it, if hey do great I'll enjoy it. But I do know one my players will have a fit if Vapaad is introduced due to how windu was so selective with who he taught it too.