Larry, now that my 4-wt is a 2-sport player, a la Deion Sanders or Bo Jackson, the price has been upped considerably. ;)
I grew up with an old South Bend glass 7-wt that I used to catch everything from trout, sunfish, and largemouth bass in fresh water to yes, believe it or not, dolphin (mahi-mahi) in the salt. Simply using a light leader as you mentioned should do just fine for less-finicky stocked fish (I don't know if the Walden pond fish are natives or stockers). Well-fished waters with more selective trout are another matter altogether.
And I don't know how far past Morone saxatilis your Latin goes, but to be a real trout guy you'll have to brush up on both it and your entymology!