As the title says

7951183
So then he, his wife, and sister would all be alicorns ?

Are there any other Stallions that you think should have become an alicorns ?

7951183
We could have expanded on the Crystal Empire and The Crystal Ponies simply by highlighting and answering ever-so-obvious question: "If The Crystal Empire was being occupied, and Cadence was a member of the original Imperial Family: does this mean that there were other Imperial Refugees that were living in Equestria?"

This would have served to expand upon The Crystal Ponies by answering "Yes"; which would lead to even further questions about the nature of Crystal Ponies and what sets them apart from the other Three Tribes aside from them having a different color palate and visual effect to them. That the Crystal Ponies are actually the MLP-equivalent of Cyborgs: who used advanced crystalline technology in order to adapt to a cold environment that is uninhabitable by normal Ponies and that 1000 years ago because of this biological difference coupled with stress brought on by the recent fighting against King Sombra; it caused a number of Equestrians to view the Crystal Pony Refugees as untrustworthy which wound up causing a number of sociological problems in Equestria.

A minor change like this would spiral out into a greater change of the narrative and a recontextualizing of a fair number of characters and their interactions with each-other:

• Celestia having grown insular that it allowed for racist elements to take root in Equestria that saw the Crystal Pony Refugees becoming little more than Second-Class Citizens.
• Luna having spearheaded a number of public reforms to help protect the rights of Crystal Ponies; which went up in smoke following her transformation into Nightmare Moon that it left the now-vulnerable Crystal Ponies to the metaphorical wolves.
• Queen Novo taking pity on the Crystal Ponies after having maintained a degree of contact with the Imperial Family; only for a peaceful meeting between The Imperial Family and the Royal Family to end in-disaster when Celestia Zealots attacked the delegation: resulting in the deaths of the Imperial Family and Queen Novos' Lover/Princess Skystars' Father: causing the relationship between Mount Aris and Equestria to have been strained.
• Mi Amore Cadenza randomly appearing close to the modern day is because of her being sent forwards in time to escape from the massacre and to lead what remained of the Crystal Ponies.
• Twilight Sparkle and Shining Armor being the ones sent to help Cadence in The Crystal Empire is because they are partially Crystal Ponies that were descended from generations of Crystal Pony Refugees.

Naturally, with changes like this, it would have also helped to better flesh out the Crystal Empire and its' culture as-it-were to have the Crystal Ponies possess their own unique dialogue and expletives. For instance a Crystal Pony might say "Coke You!": as-in reference to the Coking process which involves distilling Coal into fuel that leaves behind a thick tar-like residue that is called Coke, which to the Crystal Ponies is their equivalent of our "Fuck You!".
The Refugees would also have a sense of distrust or rudimentary hatred towards Equestrians; especially towards Unicorn Nobles who had originally screwed them over time-and-again behind Celestias' back that it caused most knowledge and history of the Crystal Ponies that had survived with them to be slowly destroyed. And that it would cause certain groups of Crystal Pony Refugees to view Crystal Ponies who are ignorant to their ways and culture as "Glass Ponies" instead: showing a sense of manufactured crystal structures instead of naturally-grown crystals.

7951466
maybe you should post this in
World Building

Shining Armor saving Twilight and the others and becoming an alicorn would have been cool.

I wrote a story where Shining did become an alicorn... eventually. https://www.fimfiction.net/story/246414/a-different-perspective