Actually, Shantae and Shovel Knight had more support abroad than Steve did. That, and Steve also had to compete with Banjo Kazooie as far as Microsoft reps go given that according to the Smash Ballot results for Japan, Banjo Kazooie was in the top 10
Calling Steve an indie rep would technically be a lie since Minecraft and Steve are both currently owned by Microsoft. That, and I fear that most people who voted for Steve were doing so for the sake of memes like Goku or Shrek and not that they actually wanted him in.
The thing about Shantae and Shovel Knight is while they were popular choices within the hardcore smash community, I highly doubt they did very well at all on the ballot. Not very many people know about them, and they aren't really important to gaming. From what I've heard, Shovel Knight did not do well in Japan. This is a real problem as a niche series' not having support in Japan pretty much kills their chances in Smash. Unless they have overwhelming support like Ridley had in the US, there's is no way they'd even be noticed in the ballot. As for Shantae, she's just niche everywhere. Again, there's absolutely no way she would be noticed over other 3rd parties. I really do like both games, but I feel like they aren't important enough for Smash. I'd also like to mention Quote is probably more likely than both of them although he's not likely either
As for likely Indie reps, Steve is the only one I think is possible. Minecraft may be owned by Microsoft now, but that just goes to show how popular and influential Minecraft has been. Minecraft has a MASSIVE player base, and I could definitely see Microsoft and Nintendo wanting to add Steve. It would be good for business. As for Sakurai, I'm sure he'd be on board. He likes Minecraft and most likely recognizes its importance in gaming. Banjo and Kazooi could get in regardless of Steve's inclusion anyway. I'd consider them to have a decent chance at DLC, or even in the base game.
Then there's is also Sans. Undertale is massive, but his game came to late. I'd say he's possibly a contender for DLC if enough people ask for him.
Also, the concept of needing an Indie rep is kinda dumb. Characters should be getting in on their own merits. I don't think Steve is likely either. He's just not impossible.
Sorry for going of topic so go Ashley!