Summoner would not work with FFXIV current state.

[Speeral]

The mob doesn't "Dissapear", rather its just obscured from view outside the field and it only happens is when the spell hits the 0:30 mark.

It doesn't even need to work that way, rather the sequence could just be something that is visible on the client-side only, but I like the idea of making a solid frosted-over sphere to sell the concept better.

Im down with the total idea I just want it to fit into however the combat system evolves. So even if Shiva is summoned and has its own battle actions, as long as it fits and doesn't throw off how fights are going its all good. even if the combat area itself freezes over to allow shiva to exist and turn into a mini dynamic area would work in you're design idea. That's my two cents.