To be fair, it allows him to use a great deal of his power without threatening to reveal his true identity. In addition, the Avengers might want to keep an eye on and possibly redeem Wanda, thus tolerate her hanging around (not like they have the ability to make her go away). Plus, they wouldn't expect much of an agenda from Wanda, thus covering Loki.
It's not perfect, but it's not that big a screw-up now that all the heroes are fractured. It's more like 'the best he could do'.