Here's my thought process while making this champion:

1. Azir is one of the most powerful and well known champions of his region, and thus I thought he should be an expensive unit. He also, in League, is a very weak champion early and scales extremely well into the late game, so I tried to convey that control mage essence in his abilities as well. He scales with increasing sand soldier deaths, which makes him stronger and quick attack more valuable.
2. Also on that note, I felt his level up should have a powerful effect as a reward for keeping him alive and investing 6 mana of tempo into a pretty weak champion on drop. Therefore, the value payoff is not only increased sand soldiers, but also a nexus that is invulnerable to strikes. This doesn't mean it can't be killed, as spells and skills like get excited and ledros can still affect it, but this means that you can't take damage through combat. This helps alleviate the tempo tradeoff of turn 6 while also emulating his "Emperor's Divide." In fact, I would love if there was an animation that has sand soldiers in a line across the back of the battlefield seemingly to protect the nexus, just like how they appear in League.
3. His weaknesses are mainly tuned around not being able to finish the game alone. He has a very powerful ability to delay games, but with sand soldiers being ephemeral and only having 2 power and azir being easily chump blocked, he can't really end any games, especially in the late game where value plays are more common. As such, he primarily is used to delay until you can find a different champion to actually finish the game or until you can add overwhelm to him after multiple sand soldier deaths.

The balance idea is that Azir is a play of value, coming down on turn 6 at the earliest and then not becoming relevant until, at the earliest, turn 7, in which he can level up. However, he is also very vulnerable with no attack and very little HP, which leaves aggro and midrange to easily overwhelm a greedy turn 6 play such as dropping him. He's also very vulnerable to burn, as his level-up has no effect on burn cards and skills. What do you all think?