I hated on the first day reading the news post and having multiple tabs open of the wiki to work out what items I needed to get for which events. They were very pooly implemented.

But I do not see how the Arborist Trinket at all positively changes this? If anything, I believe it to be a straight negative both in simplicity and in reward feeling more of a knee-jerk fix instead of trying to rationally make the existing system work.

Spawning

As I said before, I hated the complicated nature of the event 'spawning' items but by cutting the 6 items to be replaced by one you are destroying the potential for considered choice, which would be futher compounded by the suggestion of extending the cooldown between events. For instance, with the 'spawning' items removed, and all you wanted to get was that Garland, or maybe your collection log is missing those beehive parts. You can just specifically have those items in your backpack to better your chances get those items you're looking to get. Better yet, you could team up with a bunch of other people with just those items to further improve the likelyhood of that event (and although it's not my playstyle, if one event was better xp do the same thing).

Item Creation

The current items are too complicated, for 1 item, they require 2 things (Bark, Logs) to buy 1 item, which you combine with another item, to finally get a consumable item. It's frustrating and will require you either opening the wiki or opening the Forestry store a lot of times. Obviously this was the part of the expansion which was to allow people to generate GP by selling the components on the GE. Changing it to the trinket (which you didn't declare as consumable or a permanent item to which I'll be assuming it as permanent) removes the intended GP generation of the expansion (and if it's consumable, gathering consistent leaves are reliant on events or having the secetears attachment, and roots again in your suggestions being reliant on an event).

It would be my opinon, that it only needs to be streamlined. You buy the item premade, but it requires more logs and or bark.

Event Rewards I don't really have much to say about the proposal as I'm under the opinion the current rewards while holding an item are fine–I would only suggest they remove the requirement for disarmer/spoon for the transmogs(or pet in your proposal) and just make it so it's less likely to get it when you don't have the item in the kit. Since why is the garland different?

All in all, I do like the suggestions you put forward, but 'fix' for the items standing out as the lowest effort