What is your opinion on taking cloaking & sensors, and giving them something like 12 levels?
The research costs go up rapidly, so its not worth researching all the way to the top, but you still have to keep one step ahead of your opponent
And before contact, you have to decide how far to go in each, and when to devote to battle techs.
"Is sensors VII enough? What if somebodys sneaking around here with Cloak VIII? Is it worth worrying about?"
With lots of levels, you can get the distinct atmosphere of paranoia
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Also, with sufficiently advanced sensors, you could detect low-tech mines, higher level mines would still be invisible, or have a super-cloak component you can add.