On a side note, Pact of the Chain really needs to offer better summons than low level familiars. Perhaps the creatures you can summon could improve at higher levels like the druid wild shapes do.
If Warlocks got the Investment of the Chain Master invocation that'd help the familiars a lot. As would getting the Sprite and Pseudodragon familiars.
Since that invocation grants them a ton of speed, lets the Warlock use a bonus action to make the familiar attack, makes all their familiar DC's use the Warlock's Spell Attack DC and allows the Warlock to use their reaction to give their familiar Resistance to an incoming damage source.
While the Sprite and Pseudodragon have attacks that poison enemies and on a failed save, put them to sleep which is a pretty significant CC effect that can be used every round (And with the above invocation... The DC is based on the Warlock's spell mod)
Another potential idea is something like what they use in Solasta, where you get a buff based on familiars (In Solasta it only lasts for 1 minute and can only be used once per long rest so is kind of trash especially compared to Blade where it gives full martial proficiency and all weapons you use are Magical so bypass resistances/immunities to physical damage) but the buffs are:
Imp: Darkvision + Resistance to Fire and Poison
Pseudodragon: Advantage on all saving throws from magical effects
Quasit: Resistance to (Non magical) Slashing, Bludgeoning and Piercing
Sprite: +2 movement (AKA 3m speed in BG3) and immunity to Attacks of Opportunity