I've been doing some testing with Modern Naya Lurrus Burn with the addition of Flame Rift from MH2. I've only played with it about 10 matches or so, but it feels great as Boros Charm 5-8. Getting to cut Rift Bolt out of the 75 feels fantastic in a meta where it feels like 3feri is around any corner. It also makes my sideboarding plan easier against aggro as I can easily look to those as my first cuts. I don't know that I'm on the right 75 yet, but Flame Rift is definitely a step up for Burn.