Delve loot will still require you to use a catalyst charge to change it to a tier piece, though, and most players don’t want to waste a catalyst charge on veteran-track gear. Same thing with GV, most players aren’t going to pick a vault reward solely for xmog unless it’s super late in the season and they have nothing else to use it on.
The simplest way is just having higher track items unlock the lower track appearances. I mean, it makes perfect sense - which is also why Blizzard hasn’t done it yet, hah.
BTW, I think the word you are looking for is “tints”, not “tents”. But tents are pretty cool too.