I was working on the alternate timeline story, where things happens slightly differently. ( Sunset Shimmer remain Celestia's the main student, Twilight is Celestia's the second student, Fluttershy stays hermit, Rainbow Dash never came to Ponyville. )
A one particular idea cross to my mind: What if Prince Blueblood was dating Princess Cadence?

*Imagine the fandom's reaction*

Yeah, the idea doesn't sound quite attractive. ( Especially as fellow Shining Armor & Cadence's fan myself. )
However it isn't impossible. Since Cadenze & Blueblood aren't related. I assume that they both are adopted.

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The origin story Twilight Sparkle and the Crystal Heart Spell has Cadance as a Pegasus who was adopted by Celestia after her ascension to Alicorn status. Considering that the story of unicorns raising the sun with Star Swirl the Bearded prior to Celestia earning her cutie mark became show canon as of Horse Play, it is very possible that Cadance's backstory may be accepted as well. So she wouldn't have any actual blood relation to Blueblood (who is supposed to be something like 52 generations removed from Celestia anyway).

Blueblood and Cadance dating could be political, it could be true love, or it could be some level in between. Considering the trend has been to have Cadance being the Princess of Family as opposed to the Princess of Love, there's some good potential for a story there if you consider Cadance's standard modus operandi compared to what we see from Blueblood in his short appearance in the show and personality expansion in the IDW comics.

It is generally considered bad from to break up an established show couple, though, so it would take some good writing to make this pairing likable.

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If Blueblood portray as an pampered noble as most people do, then the situation would be similar to "Neigh Anything" comic. Causing Cadence most likely to avoid Blueblood's proposal attempts at the Gala.
While Blueblood would try harvest the opportunity to gain the higher royal title for himself by marrying the Princess.

( While I was thinking in my story that the main character would try help Cadence & Shining Armor together, to fix the timeline. You may call it an selfish act. Since the main character isn't okay how things are and try change the timeline how he see fit. Would that make him an villain? )

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There is a Friends Forever series issue about Blueblood and Shining Armor, in which Blues is actually Equestria's top diplomat who can be extremely charming when he tries, and when he doesn't he's at most absentmindedly a jerk. So instead of the super played out fandom "stuck-up idiot so I can pour my hate on him" Blueblood, you could have an intelligent an manipulative one that can play a stuck up idiot if he decides to be nasty to someone. (Reasons why he might have acted that way during the Gala: he hates social climbers/his fangirls that much, he knows Spike and was trying to do him a favor, he knows Spike and disapproves of Rarity from what he thinks about her. Spike is known to have connections with important Canterlot ponies.)

So he could be nice and good and all that junk if you're close to him, but awful if you aren't. Similar to Gilda, who is also a good loyal friend but an asshole to strangers. This allows him to be believably close with Cadance while still being a rather bad person.

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That will be helpful to know.