I think you need to be very careful at which tables/games you decide to utilize this concept with and how. It has strong storytelling potential and aligns suitably well with a setting framed around the traditional Law vs. Chaos setup; this is idea is prominent in Three Hearts and Three Lions and Moorcock's Elric series, both being prominently featured in Appendix N as part of the history of D&D. The warden's presence, in my opinion, should not be used to undercut the achievements of the party or make their victories feel hollow, but it should encourage them to think more deeply about their role in the setting's cosmology. However, because the warden is explicitly guarding a moral axis rather than an ethical one, the setting may have a natural tendency towards entropy until the warden is confronted.

If players pass through the world as questing heroes doing whatever they please in the moment, the warden will likely have little effect on their disparate, individual adventures, diluting the reason for including it as a mechanic. However, if players try to establish themselves as their power increases (i.e. domain-level play), they will be inherently opposed to the warden's will since they are now operating as a locus of law and stability. As long as there is a way to deal with the warden in a way where the party is able to make a meaningful choice, then there should be no issue. On the other hand, if booms and busts continue to occur regardless of their attempts at stabilization, they may become frustrated with what they perceive to be a lack of cosmological agency.

The presentation of this supplement is clean and easy to follow, no notes there.

This fits perfectly into my DCC games, with the cosmic conflicts and the element of change. It gives me the idea of creating a faction or even a deity for the Wardem. 

It also reminds me of the I Ching, the book of mutation. Excellent proposal and recommendation.

Neat idea. A touch of whimsy is always appreciated.

Original idea. I like the prompts in the boom / bust tables. The writing is clear and the choice of font and layout makes it very easy to read. I wish you utilised the available 4th page and fleshed it out more context and details. 

Interesting idea, both an agent for change during the game itself as well as a device for introducing twists for the GM.  If nothing else, using the warden should shake things up. Thanks for this
 

Interesting idea! 

Interesting. This feels less like a supplement and more like the main driver behind a campaign. My instinct is that the players would want to investigate if their plans keep getting undercut or expectations get subverted constantly by some mysterious force. And I think the Warden needs to be defined and slowly revealed as the PCs look into what is going on. Some caveats but still an interesting idea worth trying sometime.

I like this. A nice thinkpiece. It does something that many worse things don't do: give many examples. If you only give three examples of something I'm probably gonna assume you can't think of any more than those.