In my 28G Nano, I kept a Blue-Dashed Blenny for about a year. He shared the tank with a Yellow Watchman Goby and Tiger Pistol, both about four or five years old.
I believe I killed the Yellow Watchman Goby earlier this year when I re-arranged the rocks. I replaced him with a Wheeler's Shrimp Goby which immediately took to the Tiger Pistol. The Blue-Dashed Blenny and the Gobies had no issues with each other ever.
I missed having a Yellow fish in the tank, so I added a Gold Midas Blenny a couple months ago, knowing that I may have to remove one of the Blennies in case they didn't get along. The two Blennies turned out to pretty much ignore each other most of the time. There's a little fussing between the two during feeding time, but no issues otherwise.
Shrimp Gobies stay pretty close to the substrate. I believe the Flametail Blenny is of the Ecsenius genus, which prefer to hang around a little higher up. I'm not sure how aggressive Flametails are in particular, but I would chance it if you really want a Shrimp-Goby pair.
I think a bigger concern would be the bio-load of your system. My 28G is stocked to capacity, but I have about 40 lbs. of rock, I dose carbon and have solid water circulation and a decent skimmer. Make sure your system can handle the increased bio-load.
