Don't mind me posting this three years after the topic, but ultimately a lot of the replayability of Fire Emblem is seeing how the strangest units blossom or surpass ordinary expectations. Remember Bartre, the garbage Fighter in FE7? I almost always take B route, plop a speedwings on him, and go to town with bow rank. In one of my runs, I one-rounded Zephiel with him via Murgleis. Sure, there's standard and reliable units for a team (especially Milady, she's so absurdly good), but try out the underdogs. Fae can staffbait; Elen can reliably cap luck; Barth (if you're patient) can solo the second Sacae chapter. There's usually something you can change up to make your runs more memorable.