The idea of capes is a very good idea, but I've always wanted to wear two capes at once. I believe that hybrid capes would be a good way to boost engineering skill. The hybrid shouldn't be as potent as the original cape or capes though. There could also be enriched cape, I don't think all of them should be able to be enriched because that'd ruin their market value.
It should require a binding stone or two (depending on which one you're making) to make a hybrid cape. Enriched Capes should take two enrichment stones. I have comprised an example of an enriched cape and a hybrid cape's ingredients.
Cape of Protection: Gives Immunity to BroD and BoD; Gives the wearer +6 Magic Resistance
Required Materials: 1 Warlock's Cloak, 1 Cape of the Unbreakable, 2 Binding Stones, 20 Energy Essence
Knowledge Needed: Cape of Protection
Recommended Engineering Level: 45
Engineering Experience Given: 2500
Food Subtracted: 40
Weight: 22 EMU
Enriched Fast Regeneration Cape: Gives the wearer the ability to recharge health/mana at 5x normal rate
Required Materials: 2 Fast Regeneration Capes, 2 Enrichment Stones, 50 energy essence
Knowledge Needed: Enriched Fast Regeneration Cape
Recommended Engineering level: 65
Engineering Experience Given: 2000
Food Subtracted: 35
Weight: 5 EMU
The Enriched Cape idea might not be so hot due to the perks that already give the Cape effects, but I believe that Hybrid Capes is a very good idea and could be added onto a lot. Not all of the Capes should be able to be put into a hybrid cape, though. I had some trouble coming up with names for the Hybrid Capes, that was the only trouble I had with this idea.
I also didn't put in any nexus requirements due to the fact that I didn't know what nexus would be required to engineer other futrue items such as the Camo Cape. There should be some nexus requirements for these items I would think.