Blue
Ravenous Bugblatter Beast of Traal
That's what I would do: delete Divine Smite. The preexisting Smite spells already fill the gap perfectly, while they were largely redundant beforehand.
As long as "fill the gap perfectly" you mean "don't do anything like it".
The existing smite spells take up concentration, so the paladin can't use other concentration spells. They take a bonus action to cast, where most of the ways that melee combatants get extra attacks uses the bonus action so you are denying them the options of all other weapon users. The smite spells applies to your next hit so they can't be applied multiple times in a round and you can't use it on AoO and your normal attacks.
Some of those may be benefits for you, but please don't make the false comparison that the smite spells and divine smite fill the same gap.
I play a paladin and I do use the smite spells occasionally - the extra rider besides straight damage can be quite useful. But the action economy of using my bonus action doesn't fit will with my feat choice of polearm mastery. If we adopted your draconian change, my choice would be to ignore my feat and use one smite a round, putting me well behind the other weapon users in the party in terms of damage dealt and needing to expend daily resources to do it, or to ignore the smite spells completely and do really lousy damage compared to them.
All of that said, all long-rest-resource users do better if there are only one or two encounters per day. The paladin isn't particularly egregious in that regard, full casters are likely worse. On the other hand, given the limited number of spells they run out well before 6-8 encounters per day. A 4th level paladin gets 3 divine smites per day, assuming no spell use. That's 6d8 extra damage for the entire day, a bit more against specific foes. While you can't actually break it up this small, that's 1d8 or less per encounter for 6-8. At 8th level it's less than 3d8 per encounter for 6-8/day. Consider a rogue of that level is doing +4d6 sneak attack per round, say +16d6 if they use their SA four rounds in an encounter.