Hence the signing, and likely one or two more - somebody has to be the first one. Inexpensive MOR innings-eaters in the event that the young guys don't prove ready prior to one or both of them being traded.
The ideal scenario would be that Folty somehow developed command, Banuelos stayed healthy, and that Jenkins, Newcomb, and Sims took that final step by the time those guys were dealt. However, it would be ridiculous to expect all those things to happen and that you could finish the season with a rotation made up of some combination of Newcomb, Folty, Banuelos, Wisler, Sims, Jenkins, Perez, or Weber. It would be great if that happened, but to this point the only one of those to have demonstrated he's capable of making the necessary adjustments to remain in a rotation at this level is Wisler. They're probably OK with Perez and Weber taking their lumps since they don't appear to be long-term pieces, but that only gives you three starters.
Coppy's statement that they're not going to "tank" signals (to me, at least) that they're still going to make everyone earn their spots in the rotation rather than just help fill it out because they don't want to spend money. Folty will have to locate better. Banuelos will have to stay healthy. That's just to knock Perez and Weber out of the rotation right now. Norris adds another hurdle for them.
The most ideal signing targets IMO were Colon and Latos. It still makes sense to sign at least one more veteran, even if it's not one of them. The fact that Norris was willing to sign this early for this cheap likely surprised the brass, so they pounced to leave them more funds available for other things. Latos would provide the upside (and potential trade value) signing. I'm just really partial to Colon because I think he'd be perfect for all the young guys to watch every time he goes out there - he's by far the best example of how important locating your fastball is to success. If Miller could command his as well, he could be an "Ace", and Folty would benefit substantially from watching him. They all would, but those are the two that would probably benefit the most.