Presumably he'd be arriving to compete for the RCM role.
I've always liked the look of him, he uses the ball well, is tidy in possession and has good footwork. His stats have been very strong this season. Relative to the league; third most chances created, second for long passes, ninth for successful crosses. He's also registered 10 assists & 5 goals this season.
He lacks the physicality, speed and dynamism of Eberechi Eze, who plays the same position(ish) for QPR.
Swift's always looked a little lightweight & I don't recall him putting much of a defensive shift in for Reading. These areas would concern me as the strength & athleticism required to shine at Premier League level are much greater than the Championship and have surprised me this season. They are also mandatory to perform the RCM role in our system.
I guess the word of caution would be to acknowledge how Luke Freeman has done this season for us.
He had similarly impressive stats in the Championship & has hardly had a look in (rightly or wrongly).
At anything less than £6m (L Freeman numbers), Swift would certainly improve our squad & I would definitely support the signing. But given that we're likely to be selling Lundstram, I would hope for better to come in and immediately improve our starting XI.