Well for Init Boon Points, I was figuring that an init of 30 would trigger the first one, 40 the second, and so on... Keeping it pretty simple, since it would take an explosive roll to actually get 30 or above in all but the most extreme instances.
The idea of allowing these Boon Points being used to gain additional Action Points is an extremely good one, better than my idea of allowing them to be used as generic Boon Points for whatever action(s) might be being performed..
Hmm... in fact, it works well with the idea of declaring actions before rolling init as well, as it simulates (sort of) reaching a state where mind and body work extra hard to achieve that state where things seem to be moving more slowly than normal, where it seems like you have extra time. You don't realize it when you decide WHAT to do, only when you go to do it (thus you end up with one or more unused AP at the end of the round, which lets you maybe move a little extra that first round, but better comes into play later on....
If I add this as errata, I als think that I would recommend that GMs not use this for average monsters, but only for those really special ones (i.e the big bad of the adventure).