The route from Almería has a lot of physical challenges, which is a big plus for me. I basically agree with @C Clearly´s assessment of the challenging parts. The rocky river beds were the most negative feature for me. But there were also lots of hours spent walking on beautiful flower filled paths (the days around Campanario had by far the most spectacular wild flower displays I’ve ever seen), through olive and almond groves just starting to bloom or blooming, Lots of castles to explore in the afternoons, some of them are amazing, like Moclín and Alcalá la Real. The three days from Guadix to Granada were just gorgeous, lots of walking on ridges with views of the snow-covered Sierra Nevada. Guadix, Granada, and Córdoba are well worth many hours.
Assessing difficulty is oh so idiosyncratic, but I do think this is one of the more challenging caminos. And we had perfect weather, just one short hail storm, no big heat waves. Even straightforward easy stages become challenging in extreme heat, pounding rain, etc. The best way for you to get an idea of whether it would fit within your comfort range would be to compare elevation profiles from the Mozárabe with elevation profiles from days you have walked on the Francés (The Mozárabe guide has profiles for each stage, and gronze has profiles for the Francés and many others).
https://drive.google.com/file/d/117YJXBsekDSnhYwWKNR3MzQFhORECRSe/view
For me, getting up and going on the road early is a huge part of the enjoyment., and also makes the stages much more do-able. I love early morning walking and was usually on the way by 6:30, having had a coffee in my room with my coil. Those who like café breakfasts can’t do that of course. It meant that most days I was at my destination in plenty of time for a shower and then menú del día lunch, and hours in the afternoon to explore the towns.
This camino is the polar opposite of the Francés in many ways and may be a shock to your system. The Vdlp from Sevilla would be a more gentle transition. Another option would be the shorter route from Málaga, which Maggie’s blog also covers during an earlier year.
If you are set on starting in the ocean, there are a couple of other options. One, which I haven’t yet walked but hope to soon, would be the Lana from Alicante. It does not have all the ups and downs of the Mozárabe, and may be even less traveled, though. But the blogs are positive and pictures are very beautiful. Another would be starting in Llanca, on the coast north of Barcelona on the Cami St. Jaume to Montserrat, then on the Catalán to the Aragonés. That is a gorgeous camino, but it would be very long to go all the way to Santiago and puts you back on the Camino Francés at Puente la Reina. What we did then was hop a train to Ponferrada and finish up on the Invierno to avoid the Francés, but transport to break things up may be a dealbreaker for you. And finally you could start at the mouth of the Ebro, up through Zaragoza, then onto the Castellano Aragonés at Gallur, and into Burgos. But again that would put you back on the Francés, and avoiding the Francés seems to be high on your wish list. Oh, and I didn’t mention the Levante. Now that is a wonderful camino, probably about 42 days or so. Starts in Valencia.
I don’t mean to complicate your life, but if you are going to take this big plunge, you probably want to explore all the options, and there are lots of other ocean starting points!