I'm glad you like the idea. I wish more people would, because we've been asking for it for many years.
There is a downside. The downside is that if the money, instead of going into that side fund that could be withdrawn, goes into the real fund, then it would sit as extra surplus. If markets turn around and you go from $105 to $135, and there's extra money to be distributed as maybe contribution holidays, which are very small, we have accessing surplus or benefit improvements.
So from the members' point of view, they probably like having extra cash there so they can bargain for that. What we're saying to them is that the employers have tended to put as little as possible into those funds for that very same reason. They don't want the extra money to sit there and have to be bargained for. This has led to extra risk being imposed on employees and retirees, because employers were not incented to fund more than a strict minimum.