Hi Lenard,
You mentioned building and installing from source with respect to poor results from linuxpackages.net. The overall opinion here at LQ is that slackbuilds.org is top rate and slacky.eu is not far behind. linuxpackages.net is considered a distant third choice by experienced Slackers. Most or possibly all of the packages you mention are available online as packages or build scripts to build packages. Most Slackers build their own packages but they use package management rather than build and install from source. I think links to build scripts (slackbuilds.org or slacky.eu) or pre-built packages (slacky.eu) would be more palatable to many people.
You mentioned creating a /usr/local/share directory. Although end-users are free to configure and use their computers as they wish, that advice conflicts with generally accepted standard Slackware practices. The general Slackware principle is to install to /usr and to use the appropriate environment variable in build scripts to ensure that happens.
You recommended a fast computer. I agree that faster is better for certain tasks, but I would not etch that criterion in stone. I have a spare 350 MHz PII box, with 448 MB RAM, first generation AGP card with 16 MB RAM, and 100 MHz FSB. With that box I can play standard definition videos, DVDs, and DVD ISO images just fine. Playing videos is not as hardware intensive as recording and transcoding. I think readers should be told about the distinction.
You did not mention rebuilding K3B. The stock Slackware K3B package is not built to work with all the packages you recommend. K3B must be rebuilt after installing those packages to take full advantage of K3B.
Regarding hard drive space, posting some basic estimates would help many people. For example, in my experience a two-hour standard definition over-the-air TV recording requires about 2.5 GB of storage space. A two-hour high definition (720p) over-the-air recording requires about 12.5 GB. Twenty episodes of a standard definition series would require about 50 GB of storage while 20 episodes at 720p would require about 250 GB. A typical standard definition (480p) dual layer DVD ISO image requires about 6 to 7 GB of storage space while a fully packed dual layer disk requires close to 8GB. Recording TV might be beyond the scope of your tutorial, but the numbers still provide readers an idea of the required storage space.
I hope this information helps.