There’s both pros and cons to this idea.
It wouldn’t be too much of a stretch to suggest this, since it almost seems like Obi-Wan was trying to communicate with Rey during her vision. You can hear old Obi say “Rey” and young Obi say “These are your first steps.”
You might could subtly add Obi-Wan’s line regarding the Force having a strong influence on the weak-minded right before Rey tries to use a mind trick. I’m not sure where Yoda’s voice could be added besides the Force vision…
Maybe instead of hearing the sound of a child (young Rey) crying in Maz’s castle, Yoda’s voice could be calling her towards the lightsaber. Though this could take away from her hearing her own cries and what that means. Though I’m not sure how it is related to the saber exactly, but it could just represent its connection to the Force and the past, both to Rey’s and the Skywalkers’.
When Kylo and Rey are clashing sabers, maybe one of their voices could be heard saying something while Rey’s eyes are closed. Like, Yoda or Obi-Wan saying “Let go [Rey].”
I think these type of additions shouldn’t necessarily be blatant, but they could hint that they are taking an active role from the netherworld.
Though one could argue that this could take away from Rey’s own agency, since she would be basically getting help from others. But if you just simply replace the apparent “will of the Force” with the hint that is Yoda and Obi-Wan, you wouldn’t be making it any more Deus Ex Machina than it already is at least, if that is how one interprets it.
And at least now it is other characters that are driving these moments rather than the Force in a very ambiguous way, if that makes sense. Also, if you make it seem that Rey has a choice to listen to them or not, then I think she would retain her agency.
Regardless, I think one should also look at Rey’s abilities from a narrative and thematic perspective. You could argue that Rey is a fast learner because she simply just believes in the Force enough that she can do it. She doesn’t have the same kind of self-doubt that young Luke had. And Rey is demonstrated to be a good fighter, so her being able to get the hang of a lightsaber quickly isn’t too much a stretch either. Once you know how to tap into the Force, it can help control your actions while also obeying your commands, like Obi-Wan said. So her being good at various things is basically her partially letting herself go and letting the Force guide her.
Actually, this interpretation isn’t really far off from your Obi-Wan/Yoda idea, so you could go with this approach and argue that they are just an extension of the will of the Force, acting on its behalf.
I would interpret this as Yoda and Obi-Wan guiding Rey to connect to the Force, rather than Yoda or Obi-Wan acting through her directly. The Force is flowing through her, and Yoda and Obi-Wan are now one with the Force. It is both controlling Rey’s actions but also obeying her commands. In a way, adding Obi and Yoda’s voices is merely giving the character of the Force a voice.