That Homie is 100% useless when Akainu forces it to move the same way Nami forced Zeus' "body" to move with her Lightning attack. Sure, she can make the Homie, won't make a lick of difference when Akainu still has complete control over magma.
Nami never did anything to Zeus himself.. she kept filling him up with her weather eggs and then used said weather eggs to trigger the lightning attack.. it's not like she was actually able to physically move him around the sky telepathically with her hand or anything..
That being said, we actually have no proof at all about what would happen if a Logia user tried to manipulate one of Big Mom's Homies.. for example, we actually don't know what would happen if Sabo tried to use Prometheus for an attack of his own.. since Prometheus is purely fire... (like I said earlier the Nami and Zeus situation was very circumstantial and different of course since Zeus is a thunder cloud, not just purely a lightning bolt.. and obviously Nami isn't a Logia user like Enel.. what she did was plant her own weapons into Zeus and then activated them when she wanted to.. she never actually controlled Zeus the way BM does.)
Bottom line is we have zero evidence or proof of what would actually happen if a Logia user tried to manipulate one of Big Mom's Homies.. they might not be able to since it has BM's soul in it and is now apart of her and under her control..
So since all we can do is assume, we'll just have to wait for now until Oda actually shows us what would happen before we can speak factually on this..
I like the idea though and it's an interesting, thought provoking idea that Love Cook came up with.. Hopefully we get to see a strong Logia user like Akainu actually go up against Big Mom for real..