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An explanation for MMC Deathsaurus' weirdness from (I think) one of the MMC guys.
TL;DR: They were working on a G1 Deathsaurus before IDW Deathsaurus was even a thing, then when he appeared and Planet X announced they were making one, MMC brute-forced some IDW elements into it.
Sounds like there may not be a G1 upgrade kit since it would be more complicated than on Carnifex, and if anything it'll be a full special release figure.