Sorry, but you're ideas here are clearly not valid, as they all rest on intricate and baseless assumptions.

"My power is my life"; pure imagination.

JME doesn't work; pure imagination.

Square intentionnally deceiving us to think that Edea is no longer a sorceress; nonsense.

Rinoa only having Adels' powers when going to future; pure imagination.

Since your whole intricate idea is based on those notions, it follows that the idea itself is pure imagination (and pretty nonsensical too). Ultimecia's motives for wanting to compress time are almost certainly based on a combination of wanting to change her fate, wanting to get revenge on those who persecuted her, and becoming all powerful. Simple as that.