The 28-year-old has been on indefinite leave from the Ospreys all season but has been backed to return in time to force his way into Warren Gatland's 2011 World Cup squad.
And Plumtree, who lured England international Andy Goode for a stint at the club earlier this year, admits he would be delighted to help Henson get back on track
Plumtree said: "I don't want to cut across the Ospreys because I know some of the people there. But if Gavin senses he needs a change of scenery he is welcome to come over here.
"He can give me a ring and we will see how the land is.
"The Super 14 would suit a flair player like Gav. He is a fantastic talent, someone who is too good not to be playing rugby.
"If there's a contract in place, that complicates things. But contracts don't always last.
"I'm a fan and always have been. As a youngster he could do things on the pitch that hardly anyone else could do.
"In one game, I remember him spinning around and planting over a drop-goal from near the halfway line. It reminded me of Naas Botha in his prime."