I don’t quite understand what you mean. You can control the horse with a saddle, it’s not like a pig where you can’t move on it. If you’re talking about when you dismount the horse and are teleported a block or two away from the horse, I also don’t see a point of it needing to turn into an egg. If it’s two blocks to the right of you, you can easily mount it again.
A few questions I have about the idea in general:
• How would this work? (Craft a mob egg?)
• How would this be used practically? (A scenario)
• Why is this better than alternative resolutions? (Why can’t you just use a lead?)
In general, I don’t understand this suggestion or why it would be nescesary. Leads are still craftable, and you can transport animals like that. As stated above, it does also break the vanilla-feel to Elite Survival. I will be voting a -1.
If you do vote an “I disagree,” please state why, so I can reasonably argue my side.