Technically it is possible to include weights and italics inside the regular font as stylistic sets. But if the software that uses the font doesn’t recognize OT features, you’ll have a normal typeface with no access to anything else.

If you use the font in a software that does recognize OT features, then your weights and italics could be lost if at some point you decide to switch to any other font.

It is possible, but why would you want to do that?

My reasoning was that one single font file would be more efficient than 6+. My fonts folder on my machine is a labyrinth of files and folder and I wondered if anybody had done this.

I was also curious to see if anybody had done anything slightly unorthodox using opentype features.

Thanks for the response.

Sorry for being too obvious, but a good management font software seems to be a better solution for that.

I was also curious to see if anybody had done anything slightly unorthodox using opentype features.

http://www.typetalkfonts.com/typetalk_demo.html
http://www.p22.com/products/musicpro.html
http://new.myfonts.com/fonts/shinn/duffy-script/

There can be use for such a thing. An educational publisher in the Netherlands has a special writing system. In the example you can see different kind of 'i-j' ligatures, The so called IJ of ij in Dutch. Depending on the position, ij.begin, ij.alt1-3 or ij.end is used. In this way al characters can be connected.
In this writing method, there is also an example showing how a character should be written. These characters (and the 2 thin ones) could have been placed into another font, but that font wouldn't have the joining character. That might cause some confusion.
With this font the designer doesn't have to switch between typefaces. If they want to show a single character, the normal version is selected (ij). By choosing the appropriate stylistic set, they can have the version with the arrows (ij.arr) or the thin version (ij,thin or ij.thin.arr). The font also contains special symbols in other stylistic sets.
The feedback from the people using the font was that this system worked much easier and with hardly any mistakes, when compared to all the different fonts they used in the past.

Just for the record:
 
The ij-variants shown here are part of Pennenstreken, a writing method for primary schools. More than fifteen years ago –when we still did work for third parties– this system was digitized at the Dutch Type Library for the publisher Zwijsen.

Wow! Interesting reading and links provided! Thanks a million. This is what I was looking for in terms of what’s out there. I’ll continue my research and post any interesting finds here.