It's almost impossible to say but if I were him, I'd get rid of a few teens (Duncan, Ruby, Ricky) and have Seth and Esther get more involved with Bart and Sinead. Not sure where Jason would fit in but he would in time... or you could make a storyline that Bart cheats on Sinead (with Jas), but whilst has feelings for Jason, can't get over his situation - meaning he keeps running back to Sinead.
Bit like John Paul and Craig, really, what I just mentioned, although, GID instead of gay.
I'd axe Suzanne and the twins (pointless bringing her back. I love the character but the show's moved on without her and I hate that Darren's got kids now).
Axe Kathleen and let the McQueen's be a decent family without her always being there to twist things even further. The thing with the McQueen's is they can naturally make a situation worse and worse without having a character like Kathleen push them along. Also, I love how they all pull together and care for each other, Kathleen being there ruins that a little bit.
Axe Gaz & Pete. I hope Pete's only around until Brendan's reveal but it's not looking likely considering he's headmaster. He offers nothing to the show and as for Gaz, I have no idea why he's been brought back. If they wanted Heidi to have an affair, they should've used an existing character or bring in someone new - someone a bit older, more realistic..
Axe Noah and Ethan. Can't really see these characters going anywhere so just axe them now. Noah can't act, either.
Make Liberty a student and give Jamil a bit more screen time.
Lee, Leanne, Liberty, Doug and Jamil all to live in the Halls freeing up the house Ethan/Doug/Noah currently share (but don't bring in any more families).
Before axing Ethan, Pete, Noah & Gaz, I'd involve them all in the Brendan reveal.
The above four plus Amy, Rae, Ste, Brendan, Cheryl & Warren are on location when the reveal is revealed in a dramatic style. Can't be bothered going into detail but it would result in Ste, Brendan, Cheryl and the 'already' axed four dying (only Rae, Amy & Warren would survive) leaving Amy, Rae and Warren with a massive secret... Will any of them crack?
I've axed half the village!
As for keeping & bringing back - keep the rest of the current cast and (with all the axing I've done) bring back Katy - Warren's sister - who, at first, is just visiting him but decides to stay.
Bring back, Zoe, Mike & Kris. Mike's got Amy in the village still so would fit straight back in, whilst Zoe still knows Nancy, Mike, Amy & Kris. Kris would also have Zoe, Mercedes, Cheryl, Lynsey... so it's not like they'd be completely lost with the "new" Hollyoaks.
Of course, I/BK could only bring them back if they were willing to return and considering they all left quite recently, I'd guess their answers would be no