Umm, yes ?

There is no such thing as 'best practice'. Only what you are happiest using.
If that's all it takes to save your own modules and use them in scripts. Then that's going to be extremely useful.
The only thing I've used like that so far is the write.scad module. I actually made a different one for each font and renamed them for the font names. so i can just use: use <knewave.scad>
To use the knewave font. Makes things a bit easier.

Using a library of your own modules would make for simpler looking scripts, that's for sure.

Also you're rotate extrude module just makes a bog standard straight sided ring. Shouldn't it make a round sided 'donut/torus' ?

Here's some homework for you OME - find a decent module I can make different sized screw threads with. I've so far not managed to find one that actually works.