From the lore, and assuming that the "Aliens that are coming" are indeed the Thargoids, then here's what we know.
- They live, or once lived, on Ammonia worlds. Their biospheres and ours are mutually incompatible.
- They are insectoid, so I believe the adjective you seek is "chitinous" rather than "scaly".
- They are eusocial, having a "hive mind", not entirely unlike bees, ands and other eusocial insects familiar to us on Earth.
- Their technology is considerably in advance of ours, at least in terms of weaponry and stardrive tech - they can both outrun us and outgun us.
- We only won the last war against them because we "cheated", using biotech.
From these known facts, we can make some reasonable conjectures.
- We cannot terraform their worlds, and presumably they cannot thargoform ours. So any potential future war will not be about "Lebensraum", since neither of us can leben in each other's raums. Mass enslavement is also an unlikely outcome, for much the same reason: maintaining control over the slave planets would be prohibitively expensive. The motivation for war will therefore be different: resource control seems possible, but I think a mostly empty galaxy would be big enough for the both of us for quite some time to come. The only other option is irrational xenophobia: we think they're icky, and they think we're icky.
- They have no innate understanding of human concepts of "freedom" and "individualism". They may have come to some theoretical understanding of such concepts from their centuries of observing and studying us, but they will not find such things, and human behaviours that naturally emerge from such things (such as "treachery" and "double-dealing") easily understood.
- They will therefore have little or no concept of human politics and factions - humans will all be the same to them and even if certain humans or groups of humans behave differently towards them than other humans, they will likely have trouble telling us apart.
- The idea that some humans would want to betray their own species and assist in their own subjugation or extermination would be literally unthinkable to them, so they would not believe you if you offered them your services.
- Assuming they have indeed been observing us and understanding something of what they observed, then the concept of the "double-cross" would have been observed by them. The plain and simple fact is, humans - either individually or collectively - are unpredictable, they cannot be relied upon to maintain a certain position. They can be all cute and friendly one day, and the next day, suddenly and without warning, they'll turn on their former friends and attack them.
Conclusion: you were born a human, and cannot choose to be anything else. No options for "joining the aliens", up to and including reincarnation, will be allowed.
