I’d say it is possible. Its hard, but possible. You’d need to put thought into exactly -how- your character’s moral compass works, as whilst it is possible for them not to be ‘Evil’, it is harder for them to be ‘Good’ if that makes sense. I have a Warlock who falls in that category, Tessarin Sunlance. Oh she was bad, she was very bad, back in the time of Kael’thas. A ‘Combat Demonologist’ She was one of his Sunfury, and gleefully summoned demons to tear her foes apart. But, as history shows, the Sunfury were on the losing side. She was narrowly spared execution, as she had had a last minute change of heart and surrendered, rather than being captured, but she did undergo more than three years of mental ‘reeducation’ (Because we know Silvermoon loved that stuff back then).
She still summons Demons. Sparingly. She understands far much more now, about how dangerous it is, and the risk to her own soul (Though how much of this is actual realisation and how much is mind control indoctrination is unsure). She has no problem admitting she is a Demonologist, however goes on to state that these days she uses her powers -against- Demons. She usually Banishes, not Summons, or she fights fire with fire, having her own Demons slay others.
I’d say she’s fairly amoral, not in some sort of daft Harley Quinn way, but more like the character I actually based her on; the original John Constantine from the ‘Hellblazer’ graphic novels. She basically is a Female, Elven John Constantine. She’ll -generally- come down on the side of ‘Good’, but she’s not necessarily a ‘Good’ person. She can be selfish, capricious, incredibly vengeful, cruel even, but if you’ve done her no harm, she won’t harm a hair on your head, and will probably defend you against the truly wicked.
In fact John Constantine is a perfect example, given that he is, by his own words, a Warlock, and does summon Demons. In fact in one brilliant novel he summons the three Lords of Hell, who detest each other (I can’t remember the name of the other two, but they -hate- Satan/Lucifer, because he’s the one that gets all the fame), and Sells his own Soul to each of the three. The Three Demon Lords love this, they’ve wanted to get their hands on his Soul for a long while now. Then they realise they’ve been tricked. They knew he was dying of lung cancer, having smoked his entire life, but they didn’t realise he had sold his soul to the other two -as well- They were contractually bound, and -had- to Claim his Soul, but to do so would cause a War in Hell, a Three Way War which any of them could lose, and the only winner would be Heaven. He then summoned all three, showed them the middle finger and said “Right. Cure my Cancer, or you get that War you don’t want”
What could the Demons do? They had to cure his Lung Cancer. I mean, they made it painful, but yeah, they had to cure it, to spare -themselves- from humiliation and defeat.
See what I mean. That’s not necessarily -evil- but nor is it necessarily -Good- Plenty of people die of Lung cancer, But Johnny Constantine doesn’t care about that, because they’re not -Him- Its all about what is good for -Him-, and if he does some good along the way, well, that’s nice.
That’s how I see Warlocks anyway. Not Good, but not all Bad.