Aren't there 3 3/4 speed and DBX cassette players about? I guess it all comes down to cash. You could always pick up another portastudio, like a cheaper new or secondhand 4 play/2 record machine.
Or why not the 8 track DAT?. I suppose whith the 8 track DAT you could record and bounce to either analog or digital.
I never came across the DAT and I don't think they were around that long too for some reason? Problem whith the 8 track DAT is the supply of those special blank DAT cassettes? Anway, why not have a portastudio that can record analog or digital onto the normal cassette? Then why don;t they do it for the 4 track reel to reel, being able to record or bounce down to digital or analog on 1/4 inch tape? Sounds fine but using it to bounce down it won't match. 
I remember there was a 8 channel VHS for a short time. Why don't teac or tascam make an 8 channel VHS recorder you can record or bounce either analog or digital too? If you borrow your parents VHS recorder it will cost you nothing.
These are nice introductory videos with some good beginner tips for incorporating equipment one may already have around. You can add a stand-alone CD recorder and reel-to-reel to the DAT and Hi-Fi VCR he mentioned. He does repeat the myth that what goes in/out of a DAT (and by implication digital in general) will be unchanged. But since most people believe this I can’t fault him or read anything more into it. And since it’s going back into analog again that will put some fuzz back on it.
Tascam portas have been around since 1979… and so have the tips he’s presenting in the video… that is, bouncing out to a second recorder of some kind if you’ve filled your 4 tracks.
There are no problems with bouncing to a Hi-Fi Beta or VHS VCR and bouncing back to two tracks of the porta as far as noise reduction… no different than bouncing to DAT or reel-to-reel in that regard.
If you have a 424 or older portastudio, he gives sound advice (no pun…)