But adding the features means adding them to userland processes. While this technically doesn't make the kernel bloated, it still means the bloated code has to

But adding the features means adding them to userland processes. While this technically doesn't make the kernel bloated, it still means the bloated code has to be run, and has to occupy L1i. Having them in other processes only means they will eat even more cpu, as you have to use time to sync the processes.