Warlock as-is tends to be considered very strong, largely because it gets 'everything', spells, high damage, strong summon, high ac and discipline, etc. A potential way to both ease that and open up the class to being able to take more of the interesting rp/utility feats would be to split it into more discrete paths, Blaster, Caster, and Summoner
Blaster Path would get the increased blast damage and access to things like precision and agonizing blast. But it would lack summons outside of spells and have standard warlock spell options.
Caster Path would get boosted spell DC's, and potentially extra infinicast spells or bonus spells known. Potentially also access to epic spells. But it would lack summons outside of spells, and only have the basic eldritch blast progression.
Summoner Path would be the one to get the eldritch summon feats, with the very strong and WoF-resistant summon. But it would only have standard warlock spell options and eldritch blast progression.
Pacts would still be handled as-is, taken in bonus feat slots and modify aspects of each possible path by providing blast elements, infinicast spells, and summon streams. And of course allowing multi-pact if they want.
Blast shape feats may be limited to Blaster path only, or may still end up as open for any path to take in case they want to, I don't have a clear answer for what would be good there balance/rp wise.
Warlock utility spells like see the unseen and otherworldly whispers could be opened up to be taken on non-bonus feat slots as well, same as Dark Invocation feats, to allow people more access to those less combat optimal feats and differentiate warlock builds more.
Also, as part of this, I would recommend removing tumble and discipline as class feats, to bring them more in line with other casters, either being squishy or wanting to multiclass a bit. Blasters would still have super high dps to act as glass canons, casters would get more spell options and potentially epic spells to help keep alive, and summoners would of course have their summon to body-block and guard them.