Seems fairly solid throughout, however I do have a few comments.
1.) A potion decanter already exists.
2.) When it comes to a veteran cape, I can support that, however it needs to be based on day the account was created not hours players(I know you said one year, not time, just had to add that though) and should be a cape that is not currently in game of Dooms choosing,, possibly with a new "Veteran" prefix.
3.) The way Decaying Avatar drops is already fair enough considering the value/amount of drops he has.
4.) We have many difficult bosses already, I think any timed special event should be focused towards skilling, i.e. shooting stars not bosses
5.) Definitely a few major ideas missing off this list, but overall fairly solid.
Overall solid list but would have loved to see a bit more detail/implementation ideas added in on the concepts behinds the ideas for a post of this size.
Good job Arteezy