Tower is fun to play but as is : useless for casual players.
Indeed, for “pro” it is interesting to show their ranks (for their videos on YT or whatever).
But for people like me, excepting getting a message saying that I am not ranked : useless.
I would suggest that reward can be based on bigger amount of XP 
Could this be possible ?
Yes.
You have three leagues.
League 1 is for characters that are below Pit 65.
League 2 is for characters that are between 65 and 100.
League 3 is 100+.
Players who want to size themselves up and see things without really breaking T4 are included then. Yes, it will be all T3 and T2 but there’s a threshold for reasonableness in competition. You don’t want something that includes players who play on Normal or Torment 1 and just idly stand around.
I said in another discussion that once they add rewards for progression, I hope at least clearing some of the milestone Tiers (maybe every 5 tiers or so) gives a hefty chunk of XP, enough for a whole Paragon or more.
Casuals should feel rewarded for their personal progression just clearing certain Tiers, and XP would be a good way to do that, given the Tower isn’t intended to be farmed.
Also, you should be able to see your rank no matter how crappy it is. If I’m ranked 50k, I want to know. Then if tomorrow I get to 40k, I can feel some sense of progression. Eventually maybe I am rank 1200 and now feel like getting top 1k is achievable.
Not knowing is a bit de-movitating. For me anyway.
Thanks for a better explanation than mine : I assume my english is not what it should be (I am french) !
Build specific leaderboards would be awesome, not sure if they should be tied to skill bar or which skill deals most damage during run etc. So you can see the original ideas people come up with in D4 and not just the same meta build on all top 1000 spots. And yes, also showing more than just top 1000.
i would not mind seeing the tower be more like a 1 character raid type endgame. they have the 2-4 main raid already, but they could expand on it via their new “tower” concept. like for example maybe the 1st level is just a test out your gear type of run and before going to the next level give the player the option kind like in inferno hoards where there are options for the floor to be full of suppressor monsters, fire/cold/poison enchanted levels, random debuff levels where speed is reduced or take more physical damage or armor is reduced, the butcher filled levels, chaos level, a random level where anything goes. something like that seems more interesting than it looking similar to the current pit. these players that really want a challenge can pick their challenge. maybe a level where duriel/andariel/or whoever is freely roaming the halls in 1 room, but of course have them be more of a challenge.
in my opinion this is how i would imagine the “tower” concept. maybe blizz thought of this idea before or maybe they did not. if they did not then feel free to imagine with me blizzard.