If that's what you want, go for it. You can coordinate his look with your bridesmaid colors and even have him dress differently than the groomsmen.
My only tip is to figure out which bachelor/bachlorette party he would prefer to attend and make sure he is invited. (If he would prefer a night out with the men over the girls night out, make sure he's invited to the bachelor party instead of uncomfortable at a bachlorette.)
My brother is going to be my bridesman! He's wearing the same thing as the groomsmen and participating in all the groomsmen activities with my FH and his friends, but during the ceremony he will be standing on my side. My brother was my best friend for most of my life and I wouldn't have it any other way!
I had a man of honor at my wedding! It worked out great! My bridesmaids wore blue and my husband's side wore jeans, red vest, and red tie. So my man of honor wore jeans, a blue vest and blue tie. He's on the far right of the photo.
I'm having my male cousin be a bridesman! I think it's so unfair to expect the groom's side to be all men and the bride's all female when there are so many meaningful relationships in our lives that are with the opposite sex whether they are friends or family. My cousin was so flattered and moved when I asked him. I say go for it!
My fiancé has a groomswoman, she will be wearing what the groomsmen are wearing (we gave her the choice between BM/GM attire) and we told her she is welcome to either or both the bachelor and bachelorette party.