Engines with lack bottom end power?

It is also completely dependent on WHAT engine you're talking about. Some were not designed for bottom end torque. Some were designed for peak torque in a higher RPM range, like for instance, some 4 cylinders. So trying to "get" bottom end torque from some engines will always be a challenge at best. Anything can be built for "more" bottom end torque, but getting a lot of it from some engines will always be a challenge, since some are simply not designed for such.