Well Sterling has to formulate some kind of plan even bounce ideas of Lucia or something.
Thats the magic of the old bastard - the better Sterling staves his off the girls, the closer he personally gets to them and breaks his own taboo barriers in the midst of this (thus despite his best efforts is achieving Hunters goals in grooming a replacement for him). Even if you can chase him off, he has already achieved his MAIN goal (his other of course is to get his own hands on the girls just like was the case with Drew).
The real bread and butter at the start forcing his hands was the fact the family are heavily dependant on the old bastards deep pockets to stop them becoming homeless and ruining the family - the fact Brenna's career is starting to really pick up means shes already financially a viable option to be less reliant on the old bastard but of course by this point Hunter now has blackmail material over the pair of them. Instead its more about trying to bang all the girls in the house/break down their barriers enough that there is no blowback on you for when he tries to use this kind of evidence against you (as in shrugging shoulders and not being offended at prospect of you banging your entire family, causing a massive rift, ruining the family and thus leaving them all easy broken pray for the old bastard to have his way with).
Lines have already been crossed so he cant exactly just now formulate a plan but instead needs to create a united front against Hunter all whilst him not realising its happening till its too late and of course keeping everyone in the family happy whilst doing so as well and this has already proven complicated as there is little weve seen of the well written girls that can be evidence of this happening at all anytime soon.
Azelia - despite wanting Mc And him her, she refuses to outright because she knows Ophelia will not approve of it and not being a housemate means shes not on sight to get drugged into continued daily build up of lust.
Catherine - where do i start? Is fiercely competitive so is already continuing to probe Sterling as to if he prefers Eva to her, is determined to beat Amber into losing her virginity, loathes his childhood crush Mallory with a passion and even gets triggered in drug induced dreams seeing Brenna as MCs dream girl of choice not her.
Ophelia - straight up has shown little desire in sharing Sterling, shes barely even accepting her own feelings regarding him never mind idea of him being with other members of her family. I guess she is pro-Sterling shagging around but only evidenced with Amber and Eva and even then flip flops on the matter routinely (cock blocking Amber after being the initiator of the idea).
Brenna - another who of course has no qualms with Sterling being with the non-relatives and of course shared him with Eva but her reaction of Ophelia kissing her to tease the MC was not a positive one. Shes even threatened him to harm should he ever dream of hurting any of her family so her stance is less one of jealousy and more of over protectiveness.
Those are just the relatives - the others could also become easily pickings for Hunter if she can prey of negative reactions of his blackmail material. Amber didnt seem amused at being spied on, Mallory clearly has grudges she never forgets EVER should you get on the wrong side of her, Eva least likely to give a fuck but will rub others up the wrong way long before she smooths the idea of such close to home harem situation into others minds and Tiff is just in the door really so zero chance she will accept even the idea of it. Yeah the MC is gonna need a plan but it aint gonna come easily nor quickly and honestly kinda has to keep going on the path of breaking down the inhibitions and barriers of the girls so they can more readily accept what the MC has been doing all this time with each and every one of them in a positive manner.