Whilst I suspect you mean that sarcastically, I think that would be a great idea of him: more tarmac events, slightly slower and at a level he is arguably proven at - would be a realistic goal and be the right place for him to improve rallying.
With the M-Sport seat, Kubica's main backer is Lotos and not sure if they'd be able to sponsor alongside Castrol on the Fords. And, if not, I'm sure Tanak is bringing more money through his mother sponsors. And you couldn't have both of them as the repair bills would be unfathomable.