This is a great topic. Can’t say I can do it!
But some thoughts.
First I think there is a big difference between solos in songs with lyrics and instrumentals. So you need to decide what you’re going for.
Second, and I don’t know how well this applies to shredder styles, but…I think having narrative structure is very important. Telling a story, knowing what emotion(s) you want to express and how they develop.
A perfect example for me would be Tunnel of Love or Telegraph Road by Dire Straits. The solos feel like stories, have huge dynamic range, and the emotions journey - from melancholy to something uplifting (as I feel it.)
Gilmour, is another good example. Apparently he jams for hours over a track, then listens to it, picks out and learns the parts he likes, and then starts to connect them into something more coherent.
The Allman Brothers are a good one to listen to as you can very clearly follow how they are developing a theme, especially on songs like Whipping Post and Mountain Jam. Blues, especially older electric blues, provide great examples of emotions, dyamics, and repetition - not doing too much, keeping close to a theme or lick, using variations in melody and rhythm, etc.
Some improvisation exercises I learned from the Justin Guitar website are one string-solos (eventually add a second string), one finger solos, and don’t be afraid of space and repetition.