Gravel bike upgrades (wheels, handlebars, stem and more!)

Hi weight weenies, aero devils and cycling fanatics!

I'm participating in at least two Haute Route events (Dolomites and Pyrenees) and two amazing gravel events this year  (in preparation for the Haute Route Gravel Epic event next year   ), namely The Rift Iceland and the Migration Gravel Race in Kenia. 

My current bikes are:
Gravel: 2019 Canyon Grail AL 7.0, with DT Swiss c 1800 spline db
Race: 2021 Canyon Aeroad CF SLX 8.0, with Zipp 404 firecrest wheels

The Aeroad (besides some production flaws   ) is perfect but I've been thinking of upgrading my gravel bike completely to a 3T Exploro or Cervelo Aspero. However, the total weight and performance gains would be quite marginal in my opinion since gravel bike are by definition pretty heavy (tires, semi self supported events, spare parts etc). The downside however would be that I would have an expensive and a bit more fragile carbon frame (compared to the aluminium now) and pretty expensive components. Given the fact that you crash more often, components wear out quicker during gravel riding, I also use this bike for bike-packing, I want to throw it in the back of a car and so on, I've decided to upgrade the Canyon Grail (the fit is also good and the 105 groupset is just so solid and indestructible). 

Components I'm thinking of are:
Saddle (Gelu Carbon Creations, already ordered from HR ambassador Tiago)
Stem, haven't looked into it yet, tips are welcome!
Handlebars, I want flared aero bars that could fit TT clip-on bars, again tips are welcome
Seatpost, getting a two-piece seatpost with a spring for comfort
Wheels, I'm very close to buying set of Zipp 303 Firecrest wheels, feedback or alternatives welcome!

To summarize I'm asking from you is, do you have any tips or alternatives for what I've stated above?! Especially for the wheels since they are quite expensive. My considerations for the Zipps are:
- great value for money (1352 grams, stiff, wide internal width, 40mm high, proper hub and general Zipp quality)
- gravel suitable but also very qualified for normal racing
- I can swap both wheels (bit more hassle because of freehub change) with my Zipp 404's on my Aeroad during days with insane side wind or climbing (500 gram lighter, potentially more due to tire choice

Looking forward to your reactions/discussion!

Ruben

Why do you need a freehub change for the Zipp 303 firecrest?  If you want to reuse your cassette with is on the 404s you can.