Sounds like a nice list of fish, not to sure if you have to put them in any specific order. You might want to keep in mind some gobys and wrasses have been known to be jumpers if you have an open top tank.
I have never owned any of these fish, so this is just from what i've heard, but those seem like they should all be fine. You will definitely need a lid for the wrasse though, they're renowned jumpers. You may get better responses in the "Reef Fishes" forum.
goby first, pseudochromis last or pseudochromis and wrasse at the same time. I have a false perc, sixline wrasse and royal gramma. I'm debating a 4th fish or not. 3 just seems right for my tank but I may do a blenny.
well ANY pseudochromis has the potential to harrass BUT the sunrise (flavivertix) it is one of the least aggressive and least likely to harrass. I've heard the theories and accounts of pseudochromis being intolerant of small wrasses but I have kept them together (sixline and neon dottyback) and seen way to many coexist to buy into it. I think pseudo's are just prone to picking on small fish and have little prejudice. I do think the max size and shy nature of the possum does mkae it more likely to be picked on. my sixline for example wont get picked on by anything remotely in the size range of himself. I've had him with neon pseudo and larger spotted hawkfish and they've (and others) have tried and failed to intimidate or put on a beat down.
I have a watchman goby and just an FYI they are somewhat boring. Mine literally just sits in his cave all day long. Every once in a while I will see him on the outside of it, and when there is food in the tank he just sits by the entrance and catches some that comes by. Also, if your thinking about doing the pistol shrimp pairing, it's hit or miss.
Only reason I am telling you this is because with your stocking list you will be maxed out on a 30G so real estate is a prime commodity in a tank that size.