To get the range of that 9x28, you'll need an 11x34. The 34 will need a derailleur with a longer cage. The longer cage will hang down further.

But I'm still not following you. Somebody has a Capreo-pattern rear hub on their folder. Shimano discontinued the cassettes. Now there's a convenient source for replacement/spares. Are you suggesting they rebuild a rear wheel with a new hub, buy a different derailleur, fit a huge front chainring...to save money on the cassette? No, seriously, I've missed your point. Could you re-explain?