Bas could easily fight at 205. However, as eager as I am to see what he could do now, he would have to go through the paces to get back into things. The MMA scene has evolved greatly since he was UFC HW Champ, and the level of competition (and skill) has increased drastically since the inception of MMA.
He's been gone for a looonnnnggg time... Over 7 years to be exact. Many greats lose a lot being away from the ring in only a fraction of the amount of time.