I'm currently playing a Great Old One (GOO) Pact of the Chain warlock in one homebrew campaign. Originally, I had designed the character to be evil and roleplay-heavy, with skill and spell emphasis on illusions and enchantments. He'd be mostly interested in just gaining power and influence under the radar.
Then, shortly before starting the campaign, the DM banned evil characters entirely. I still liked the concept, so I've been trying to tweak it. Turns out the campaign is also more combat-heavy than expected.
Currently I've got an Imp familiar, and was planning on trying out grabbing magic circle, summon greater demon, the Chains of Carceri eldritch invocation (which lets me cast hold monster at will on celestials, fiends, and elementals, once per long rest per creature), and so on. Give him a summoner/controller feel.
Thing is, I still want him to feel like a GOO warlock, so I'm interested in using a Gazer familiar instead of an Imp. Also, homebrewing Summon Greater Aberration (exact same as SGD, but for aberrations), and adding aberrations to the list of things Magic Circle and Chains of Carceri can affect.
Are all aberrations of CR 6 and below approximately as powerful as demons of CR 6 and below? Or are there any outliers that would pose balance issues if I were to summon one via a summon greater demon-like homebrew spell?