Going opt-in instead of opt-out does not change the fact that I would still have to toggle the features manually. To be more specific, my use case is that I have a program to control cameras in my lab. But not all computers have the libraries for all cameras. So, every supported library can be enable/disable using a feature But the program being still in active development, I am frequently using cargo run, cargo check, cargo install, on different computers with different libraries installed. What would be convenient would be to have a configuration file on each computer, specifying that we will build only for PCO camera on this computer, only for Photometrics camera on this one, only Ximea and PCO on this one, instead of having to remember to toggle the relevant features every time. A shell script is not very convenient because I use different commands, run, check, install etc.