I've been working on documenting the existing GameEvents system (products of this so far are on the wiki). The good FXSSSeckman has indicated that they hope to add lots more GameEvents, as the current crop were added specifically for the DLC scenarios; some aren't used in them, and thus possibly not well tested, but they were all added for that purpose. While they will, in that case, work through the game code looking for places that events should be added, it seems it would be useful to make suggestions. We might even hope that suggestions could be added before they work through systematically adding some.
On the other hand, we can assume that they won't want to add them in every conceivable place, as that will slow the game down in execution terms. As such, we should try to make sure our suggestions are good and genuinely useful, and try to avoid redundancy (not add events where an existing one can actually be used), so hopefully we can discuss suggestions, and I'll consolidate them here. In this post I will add those that there seems to be consensus on (although that consensus might be from elsewhere), and in the next post I'll keep a list of ideas for discussion, starting with my own top-of-my-head suggestions.
I'll try to cull suggestions from elsewhere, and if other people want to help by pointing me at them that'd would be a great help (as I'm not going to spend hours each day on this). Hopefully, we can suggest the following for each suggestion that's 'finalised': when it will fire, which of the categories described on the wiki it will be (hook, predicate - TestAll or TestAny, or accumulator - int or float), if it's a hook what behaviour will be up for replacement, and what parameters we would want it to take.