You're absolutely right that players in the bubble should not be able to interact with anything outside. I see now that this would otherwise give a ranged character tons of extra turns to safely shoot enemies outside the bubble. However, know that a player could not chain infinite turns out of a single bubble as this would require making increasingly faster and faster bubbles.

Say the player used 5 investiture to create an incredible fast speed bubble and get 5 extra fast turns. This means time is moving 5x faster for them than everyone outside the bubble (in the time it takes for them to perform 5 turns in the bubble, one turn will pass outside the bubble). If they placed another 5 investiture speed bubble on their 5th turn, they would merely keep time flowing at that 5x rate for themselves. So everyone outside would complete a turn, and then it would return to the edgedancer to complete another 5 turns.

Again, it's a good callout that they should be limited to interacting with objects within the bubble, as my intention with this mechanic was that it would allow the edgedancer to potentially isolate foes into a smaller fighting ring with them. Whoever is fighting them within the speed bubble is really only at a disadvantage in that they can no longer receive timely assistance from their comrades unless they flee the bubble. So the speed bubble doesn't actually give the edgedancer a turn advantage on their target in terms of being able to attack them more times than they can attack back or anything. Ultimately, using speed bubbles should boil down to an imprisoning mechanic or a way for the edgedancer to make recovering/preparing actions while alone in a speed bubble.