If level 1 is the problem...
I don't see why they don't silo level 1 differently.
This goes back to the vertical/horizontal axes in game design.
As 4e rather correctly realized, it's not a fair trade to trade one for the other. If you trade that +1 to hit for a magic missile, that's not a fair trade, and it leads to things like "I can do 1,000 different things...none of which can be effective at all at the level I'm at!"
This is a good discovery, and it deserves to be kept.
So, I guess in 5e as it stands now, if I understand mearls correctly, they think that level 1 offers too much horizontal advancement, and that future levels don't offer enough vertical advancement.
So, you have a cleric. Clerics channel divinity and cast divine magic and have weapon and armor proficiencies and maybe have feats or whatever.
The risk is that a Fighter who gained level 2 takes a level of Cleric and now has way too much at his disposal.
The risk is also that the same fighter who takes Level 16 of Cleric only gets first level magic that's useless against the 16th-level undead he's fighting.
5e is going to try and solve both problems. So if you're a 15th level fighter taking your 16th level in cleric, you can still do things as mightily as a level 16 cleric can, and if you're a 1st level fighter taking your 2nd level in cleric, you won't be doing ALMOST EVERYTHING your cleric buddy can do.
The problem can be partially solved like this: you have a character level that measures your overall vertical power. Your assortment of class levels measures your overall horizontal power.
So if you're a 15th level fighter taking your 16th level in Cleric, you'll have the same raw dice potential as a 16th level cleric (your heals will be 16th level, your smites will be 16th level, your spells will be 16th level), but you'll have 15 Fighter Tricks for your one Cleric Trick.
There is a problem with this, called out above, in that it takes some rationalization.
Wizard: "Finally! I've attained great magical power and have mastered the manipulation of reality that grants me the ability to call upon raw elemental fire! I've learned Fireball!."
Fighter: "Hey! Me too!"
Wizard: "But...I've studied and sacrificed for this moment. I have abandoned friends and family and cloistered myself in my tower...all so I can learn these secrets."
Fighter: "Ha! Silly wizard. I got drunk and partied hard and now I can do it, too!"
Wizard: "But...my life's work..."
Fighter: "Hey, don't look so down! You can still do a whole bunch of other magical tricks! Like that one where you can make a magical hand carry your stuff! And that one that keeps your beers cold! That's cool!"
Wizard: "Mere cantrips...all in preparation for this..."
Fighter: "Well, you can sit here in a stupor, I'm gonna go blow things up with a fireball. I've got enough HP, I can probably even stand in the middle of it!"
Wizard: "YOU'LL BE FRIED ALI-...wait...actually, that's far superior to my strategy..."
Fighter: "HA! You sound like a liberal arts major. All Boo-hoo, I've wasted my life, all this debt for no reason, wah-wah-wah..."
Wizard: "...all my sacrifice..."
Fighter: "Ha! Well, later! Doot dee doo!"
The above illustrates one of the more critical problems with this: you loose one of your main motivators for gaining levels. If I've been a cleric for 15 levels focusing on that awesome 8th-level cleric spell I've always wanted and Thiefy McGee comes along and takes one level of Cleric and all of a sudden can do the same thing, that stops me from feeling special. Even if I can do hundreds of other things, having that carrot shared between me and and the rogue is a bit of a bitter pill. And then you'll have the "jack and master of all trades" category, where you get a character taking one-level dips into everything and not only being a 16th level character overall, but being effectively a 16th level rogue, a 16th level wizard, a 16th level fighter, a 16th level cleric...all in one character. Okay, they can't do EVERYTHING each of them can do, but they can do at least one thing from each, at a significant level of power. I can choose to sneak attack, and fireball, and stunt, and heal and all of a sudden I am a one-person party (which isn't an undesirable result for some games!)
So there needs to be some refinement of that idea. One option is for "class exclusive abilities," things that need X levels of a class in order to open up. These should typically be big, defining things. You don't get Fireball until you've had at least 3 levels of Wizard, or something.
As for the level 1 breadth-buster, what I would prefer is instead to have special rules governing your first character level, rather than overload a class with level 1 abilities so much that it mandates you invent an entirely new table for it just to cover that spread.
So, for instance, only your first level of any particular class grants you weapon and armor proficiencies. Only your first level gives you the +1 to an ability score that your class gives you. Etc. After your CHARACTER passes level one, they don't get that from their class anymore.
That'd certainly avoid duplicating the class tables!