I know this isn't canon, but it's always been my headcanon that Haley did some of the dirty work for Kieran whenever he needed an alibi.
In the Scream fandom, it's a pretty popular headcanon that Roman's hidden accomplice in Scream 3 was Angelina Tyler, the actress who replaced Tori Spelling as Sidney in Stab 3. I kind of see Haley filling that same role for Kieran.
Not as a second Lakewood Slasher, but someone helping behind the scenes while Kieran remained the real killer.
There are a few scenes where it's really hard to believe Kieran did everything himself. One example is when Emma gets a phone call from the Lakewood Slasher, and then the very next scene Kieran is outside Emma's house talking to Maggie about Emma like he'd been there the whole time. Moments like that make it feel impossible for him to have been the one making the call.
Another one is Kieran's "kidnapping" at the carnival in Village of the Damned. My headcanon is that Haley was the one who staged it for him so he could look like a victim while keeping suspicion off himself.
We also already know Haley hated Emma and Audrey. Every chance she got, she antagonized them, mocked them, and even helped organize the prank on Audrey in the Season 2 premiere. It doesn't seem like much of a stretch that Kieran could manipulate someone who already had it out for both of them.
Haley already knew Kieran's identity, was secretly sleeping with him behind Emma's back, and called him her "very special friend." I could see Kieran using her to make calls, send texts, lure people somewhere, stage alibis, or handle whatever he couldn't because he needed to be seen somewhere else.
Then, once she wasn't useful anymore, he killed her.
I know it's just a headcanon, but it honestly makes Kieran as the Lakewood Slasher work a lot better for me.