While I understand the concern, it wouldn't bother me at all.
You give POJ and Smith a half season to see how they do. If one or both really struggle, you make a deal at the deadline. In that scenario, you likely wouldn't be looking for a lot of offense from a potential defenseman, which would keep the cost down.
Much like letting things play out with the bottom six, trading Pettersson and letting Smith/POJ both play would answer a lot of questions moving forward, either positively or negatively.