For example your RWML usage. I was never aware someone used it in the way you did in Poster 1. Luckily it worked there, I would never have expected such a complex stacks works inside Poster 1. If it is also working in Poster 2, great, even better! Please let me know if it works. Unfortunately, this is a wide range, and I cannot guarantee anything in regards to 3rd party stacks. Exactly this nesting of stacks is what decreases the performance.
Same with cookie manager. If RWML works in Poster 2 (so displaying or hiding content dependent on some outer conditional), then the cookie manager could also work, when adapted to Poster 2.
Bottom line: I see that displaying HTML content based on a cookie setting makes sense. If this cookie manager would be used inside the template, I have good hope it will direcly work. Of course this is something completely different than inside the item itself.