Here the 1841 British edition omitted the adverbial so, changing “even so as by fire” to “even as by fire”. The 1849 LDS edition restored the correct so. Either reading is theoretically possible. There isn’t much evidence for either reading elsewhere in the text. But there is one expanded form of this phraseology in 1 Nephi 22:17, and it has the so: “even if it so be as by fire”. The critical text will follow the original reading here in Ether 4:9 (“even so as by fire”).
Summary: Maintain the so in Ether 4:9 (“even so as by fire”), the reading of the earliest text.