I'm all for enderpearls, however, endstone, is a complete no, UNLESS Crypt makes the end restore periodically. I don't know about everyone else, but I'm big enough a jerk to mine all the endstone so that no one else gets it. I know a couple other people who would probably help me do this.
I'm not sure how I feel about being able to build in the end, this would permit players to build very nice grinders which would probably make enderpearl-ing around the Number 1 entry method. However, if you can't build, or there is a periodical reset, it might discourage players from doing so, therefore increasing the rarity of enderpearls.