I think the antennata lionfish, snowflake eel, and harlequin tusk are great choices that will do well together. I currently have an antennata lionfish with a snowflake eel without any issues. The antennata would have to be full grown and the eel would have to be super tiny for there to be any risk of the lionfish eating the eel. I'd just shoot for medium sized for both of those fish. I don't think you'd want to go too tiny if you're adding other aggressive fish. The antennata and eel won't be particularly aggressive in terms of fighting, so they're the ones that would be prone to get picked on if they're too tiny. A harlequin tusk is supposed to be only moderately aggressive and should be completely compatible with the eel and lionfish. Just don't get a tiny juvenile tusk that could get eaten by the lionfish. I'd go for a medium 4-5" tusk to start with.
The triggers are where I see there being more issues since they can be the most aggressive. I know someone on the forums that is doing a 260 gallon reef tank with a snowflake eel, a volitan lionfish, and some triggers and tangs. In terms of the triggers, he chose a blue throat and a niger because they are supposed to be a little bit less aggressive. From my understanding, the clown triggers and humu triggers get a bit larger and more aggressive. I think the clown trigger especially is a bad idea since Live Aquaria lists its minimum tank size as 300 gallons. Also, as Erin mentioned, there's definitely a risk that the triggers could eat the lionfish's fins. You definitely don't want to house a pufferfish with lionfish for that reason.
In terms of other suggestions, what about some tangs and large wrasses? Something like a Spanish Hog could be really pretty too!