.... It's called making FE4 into an Awakening styled game so Sigurd and co. can just come back in endgame sidequests. Even though they got BBQ'd. And breaking the plot.
Wait! How about using that old reviving stick! The Valkyrie Staff! .... What do you mean I can't revive him because he died in Gen 1? Stupid technical limitations.
Maybe you can get back on Arvis by stealing your wife back off him! Just imagine the look on his face! "HAH HA I STOLE YOUR- Hey, where'd she go?" .... Oh right, no rescue command.
How about just straight tanking the Falaflame? Averages say Sigurd's OHKOed. And having Tyrfing equipped makes that a 2HKO and the Meteors will be fatal anyway.
Alright, any more ideas?