Put nginx in front of apache and allow it to buffer responses. That way apache can move on to rendering the next request while nginix empties the buffer. Each apache process still uses just as much memory, but they can get more work done, because they aren't tying up memory while they push the buffered response out.

Most of these are micro optimizations that matter most on a larger site. Most large site do not use Apache for static content. I agree, nginx would be a better first choice for a module.

One thing that may not be obvious about minimization is that it does not yield much size reduction when coupled with gzip. You may see 30% decrease in size with minimization on the plain file, but when you gzip both the plain and minimized you may only see a difference for a couple of hundred bytes. If you are worried about speed, you should be using gzip for static content.