Yes, I can see it's not something that would be done lightly and would only occur with at least several days notice and planning (those tanks aren't going to be very useful while it's happening).
Once swapped, I imagine the engine would remain the same for months (or longer) before the need to swap back came along.
I see it a little like fitting your car with Nitrous - you're not going to need it on a daily basis, but it's damn good to know it's there as an option. Of course flicking a switch to kick in the gas is a little easier than swapping out a whole engine...
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If it moves, shoot it, if not push it, if it still doesn't move, use explosives.
Nothing happens in isolation - it's called "the butterfly effect"
Mors ante pudorem
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