I am really curious how other races joining your fortress will work. Will we be able to force certain species to show up? Can we restrict certain reactions/workshops to certain castes/creatures? Would elves naturally refuse to cut down trees or would your own ethics allow that? Not sure which is preferable. I imagine that if an elf joins an orcish fort it is because they believe in the orcish ideals. Of course, some that may join your fort may be as slaves...but they don't really get a say in ethics anyway.
Some well defined bonuses and maluses for each species. It would be interesting to be able to find an elf to craft bows for your military or maybe a dwarf to do all the wall engraving when playing as a different race. I remember Meph used to have races laid out in a number of groups where they would trade within the group and raid anyone outside the group. Would make sense to have Humans and Dwarves enter each others forts as members much more often than an Orc may request citizenship in to either. Some species may be more xenophobic than others? Or that may be something to be decided as the player.
Would be fun to play as dwarves and accept a number of orcs in to my fort and place them in their own special military unit. Also would be fun to enslave humans as miners in my own orc fort
A question I thought of while writing this out: How do attributes affect labors? Is it simply a learning rate modifier? Or is it speed? Will orcs always mine faster than elves due to their strength? What about efficiency? Will they uncover stone more often? Will crafts be of a higher quality when done with greater creativity?