Does this sequel idea sound viable for my turn-based strategy game?

The first game is Historical Conflicts involving colonial era technology, which I am mostly done making it now.

One sequel idea is modern technology, but that seems sort of drab and boring.

Another sequel idea is future technology involving an Alien Species in a civil war with itself.

What do you think about these two sequel ideas?

Does this sequel idea sound viable for my turn-based strategy game?
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