Yes that is nice that they do and as you said , they do it for te purpose of testing ...10 stars = 1 present
1 present = random selection of one thing out of everything suggested by OP :p
The diamonds idea sounds nice from a pure players perspective. However I don't know if Inno would want to give diamonds on live servers like that. Beta already gets diamonds each time an event comes 'round for the purpose of testing the event. If they started giving diamonds on live as well it might detract from that.
But it would still be nice to get that kind of gift lol....a bit of diamond dast to sprinkle and make people in my cify happy lol