Well TAB completion is part of the bash shell and FREESCO uses ash. So with regards to adding bash into FREESCO it just plainly will not fit in any way and it would be considered inpractical at best, sorry.
But there is a bash package for FREESCO that can be used on a hard drive install. But I have not tested that package and it is MOST likely that it will cause problems with the new Dropbear binary included in 034 because it had to have source code changes to run on ash in the first place and after the changes to make it run in FREESCO it no longer ran in Slackware with bash as a shell.
But as stated I have not tested it myself and if you need completion you could give it a try.
If you are afraid that you might make a mistake. The chances are high that you will never learn anything.