3. Increase the amount of metal required to build
IMO, this doesn't make much sense because it's smaller and thus would require less metal than a normal sentry, not saying they should decrease the amount of metal it takes to build one, though
I think the metal cost should stay as it is, but i agree with the other 2 things since if it's a smaller sentry, one would assume it's range would be smaller than a normal sentry, and if it's a smaller sentry, it's got smaller pieces, and thus, is easier to break
However, with such downsides, wouldn't people just ignore the mini-sentry for the normal sentry that's stronger and got a better range?