Neither needs to be brought back. Let's be honest, neither of these titles will do anything to help the undercard and I think everyone here knows it. The few that advocate the return of these titles just want them back simply because they want them back.
In mainstream pro wrestling, hardcore matches are pretty much dead and there are good reason for that. It takes so little skill to be a "hardcore wrestle" that pretty much anyone can do it as long as they're physically tough. No holds barred, no DQ, or whatever you want to call them are fun to watch as a novelty now and again, but the novelty wears off after a while if they're too frequent. After the 24/7 rule went into effect, the WWE Hardcore Championship became a running joke. It's just hard for me to look at a title that changed hands well over 200 times in the 3.5 years it existed as coveted or prestigious.
As for the Cruiserweight Championship, again, why? Weight divisions might work in Mexico or Japan but they don't sit well among American wrestling fans as a whole. To me, and a lot of others, you're saying that the little guys can't hang with the big guys and have to have their own special division where they don't have to worry about facing the big guys. For a long while, a lot of internet fans have inaccurately said WWE favors "big men". Many of those same fans will now complain when someone that's definitely on the smaller side gets a big push in WWE. Wrestling has changed in the sense that fans care more about the actual ability of the wrestler rather than his size. If you look at the WWE roster, many of the tops guys in terms of talent and/or popularity with fans lie in the 200 to 225 pound range. Daniel Bryan, CM Punk, Christian, Chris Jericho, Dolph Ziggler, Cody Rhodes, The Miz, Kofi Kingston, Santino Marella, Hunico and a few others all fall within that range. Many of the "bigger" guys aren't much heavier. Orton is in the 230s, Drew McIntyre is probably in the lower to mid 240s, Wade Barrett is only about 245, Cena's around 245 and looks heavier due to him having a stockier build. He might be at the 250 mark but no heavier than that. In the WWE, guys who are legitimately significantly heavier than 250 include Sheamus, Brodus Clay, Mason Ryan, Mark Henry, Big Show and Ezekiel Jackson. Plus, when you look at FCW and some of the more talked about talent, such as Seth Rollins for instance, are also well within that 200 to 225 pound range. As I said earlier, wrestling has changed and a lot of the better talent out there and currently coming up through the ranks are guys that are in that weight range.
I'd be more inclined to get behind creating an undercard title for the guys that are at the lower end of the rung. Something like...I dunno.....WWE NXT Championship or something along those lines. Now that NXT is basically a brand and regularly features guys on the undercard, it could potentially add something meaningful to some of those feuds.