as 引导的让步状语从句,意思是“虽然,尽管”.用法：把表语,或者动词提前,如：
Try as I might ,he would fail again.
Old as he is ,he is not good at football.
值得注意的是,如果是名词,尽管是单数也不要加冠词,
Child as he is ,he knows a lot.而不用a child.
你所问的问题中,as 的用法是一致的.而might和could是情态动词的用法,表示的程度不一样而已.
希望对你有用.全文手打.