Well ya probably gotta ask yourself by replacing just the rims - what is it going to achieve?
weight loss? - probably not much that you'll notice.
strength? - yes you might loose some strength.
By replacing both wheels inc. hubs.... yes, you'll get a weight saving...........BUT!
The standard rim/hub set-up on the tenere has been made very strong to handle being loaded up and hitting rough/rocky roads, but of course with strength comes a bit more weight with these wheels. So! if your touring around it would be better to have reliable wheels than worrying about the weight and looks of them..... IMO!.
Mate, it all depends on what your doing... like if you where going to compete in a race like JMo well then yes you'd do it, otherwise if you have got cash burning a hole in your pocket..... I take donations
If you do replace the wheels how much do you want for your old ones?
I wouldn't mind a spare set to have knobbies fitted to them
cheers
Reg.