While I certainly agree that HS needs more things to do, I think the 3rd track is the right move for the moment. I don't think Mater's junkyard jamboree is the reason DCA's TSM has shorter lines. You're certainly not "losing" anything but adding capacity to TSM. I know that to a lot of people, it's just a video game, but it's a lot more approachable than setting in your living room with your entire family with 3d glasses and joysticks all over the living room. I don't think my 68 year old dad and I are going to play Wii U over christmas, but our TSM battles are legendary.
I also think we have to be weary about what's an E-ticket these days in terms of the Disney sphere of things. The rides that Universal builds that we consider E-tickets aren't fun for the whole family, which is the problem HS already has. HS is a lot like AK in the sense that it has 1 E-Ticket (ToT/Everest) and 1 D-Ticket (RnR/Dinosaur) that people in the average travel party don't want to ride. If you're not a show person, then the rest of HS is pretty unappealing to you. If you're not an animal person, then the rest of AK is pretty unappealing to you.
That doesn't mean you just start junking up the park with spinners and kiddie rides. I liked mater's junkyard jamboree just fine, but in terms of adapting Toy Story Playland, I see big problems. RC Racer's visual impact on DHS would be just like sticking a giant blue hat on main street. No one over the age of 5 wants anything to do with ZigZag spin. (Altough, come to think of it, DLR has a couple of these little up and down rides for tykes. WDW doesn't have any). Regardless, it's not going to do anything about wait times at the current headliners. The vistas from parachute drop is appealing, but again, you have the aesthetics issue and whole "people afraid of heights" problem. What makes TSM great is that it eats entire travel parties. Nobody has a problem getting on TSM the same way nobody has a problem getting on a dark ride. that's why 7DMT is way more popular than it should be for a kid-coaster/dark ride hybrid that's way too short.
Uni is great, but WDW can't go the Universal route and just build fantastically advanced rides that are overly intense. They also shouldn't just junk up the park with primeval whirls and ZigZag, etc. just for the sake of eating volume. Get Star Wars right and, more importantly, they should make a huge investment in the show quality there. I have a friend who is so anti-ride pro-show that she can spend sun up to sun down at HS multiple times a year. I don't get it. But having seen Aladdin at DCA, it makes no sense that DHS can't make it as a theater park by upping the quality of the shows.
You have Little Mermaid, Indy, BatB, LMA, and a dark Idol buiding that could all be turned into improved, higher quality productions without you having to build much of anything. They'll eat more capacity than a ride ever could and it would give DHS a reason for standing alone. Turning DHS into DCA or MK isn't the only answer. The best show at WDW shouldn't be at Animal Kingdom