I have not looked at your changes closely, but my concerns would be the same as the last time someone proposed something similar. First, how do you decide how much domain memory to allocate? Second how is memory being managed? You actually answer the second but "no memory management" is not a very good answer !
Memory management on particular is important for any app that can run for any length of time, allocating and deallocating arbitrarily sized blocks of memory. Over time memory becomes fragmented so new blocks cannot be allocated, even though there is enough free memory.
The problem is that what you’ve done may make sense for you, but it would not necessarily make sense for other apps, e.g. apps that do not use particles or use a different approach for them.
It’s also hopefully a bad time to look at this. Hopefully as with Harman taking over AIR development we could see performance improvements in AIR which make using domain memory for performance gains unnecessary.