Sure Scizor can take care of Latias, but the OP is also worried about Kingdra, Mence, etc.
If someone doesn't like the changes you recommend, just recommend different ones that can do the same job. This isn't the era of Garchomp where you need to have a specific Pokemon to beat one other specific Pokemon. As I've said before, checks is what the current metagame is about. Just look at the top battlers of Smogon (and if you say Smogon sucks then I lose any respect that I still had for you after I saw your age :/ ) and see how they battle with their teams- switching and checks. So please stop mentioning counters, because they rarely exist anymore.
before you rate again make sure that you know that the OP doesn't have to change everything like you say, although you can attempt to convince him otherwise. You don't have to accuse him of "being immature" because he doesn't want to change his team the exact way you want him too. I mean, tbh it is his team, not yours. The OP's reasons for not making the changes are sound, so don't try to change his mind, and go for changes that work with what he wants to have.