Warlock: As an at will caster?

In 3e, the warlock class was introduced to the world as a completely new way to perform magic. It did not use spell slots that had been a staple of D&D magic for decades, but instead made use of Invocations, a system of at-will spellcasting. For the first time ever (in D&D), you could play a spellcaster who did not rely on the slow attrition of daily resources. Despite their unlimited use of magic, this class wasn’t even particularly powerful either, often placed within the mid tiers of character classes.

Well, what if the 5e warlock harkened back to the 3e warlock and became the at-will caster.

What if the spells the warlock knows were usable at will, without needing spells slots?

This at-will spellcasting would replace spell slots entirely. The warlock’s access to spells would follow the progression of a half caster; that is to say that they access 2nd level spells at 5th level, 3rd level spells at 9th level, 13th level spells at 13th level, and 5th level spells at 17th level. But any spells they learn this way would usable at will.

This way, the warlock becomes a unique and interesting spellcaster, that is actually relatively simple to play as well (aka the mythic simple spellcaster).

Sure there might be some kinks to iron out, but does this seem like an interesting way to design the warlock to anyone else?