Were it not for the threat to longevity and the reliance on community, the factor that would make or break persistent-world multiplayer-focused games like MechAssault 2, ChromeHounds, and Armored Core V is the execution. Each of these games has a different way or approaching this style of game.
What MechAssault 2 did, which might have contributed to the decline of Conquest mode, was give Conquest mode its own spot on the main menu, separate from single-player and multiplayer. This meant that it was easily passed-over by people looking for multiplayer. “Out of sight, out of mind,” as they say.
ChromeHounds and Armored Core V fixed this issue (Though, admittedly, the decision made with MechAssault 2 to have Conquest as a separate gametype was likely intentional) by making their persistent-world multiplayer the only multiplayer, with inconsequential “for fun” matches as a secondary gametype within the persistent-world multiplayer.
While ChromeHounds still sequestered its single-player gameplay away from its multiplayer, Armored Core V went all-out and integrated its single-player missions in with its multiplayer. The missions are still single-player, but they ultimately serve to help the player’s team in small ways.
Curiously, however, both ChromeHounds and Armored Core V decided to forgo non-online multiplayer. Neither game has split-screen or even system-link multiplayer, which may contribute to longevity problems. While it was a great game while the servers lasted, with the servers down now and no way to play online (Which means no way to play the real game) there’s absolutely no reason to even buy ChromeHounds anymore.
Armored Core, which has always been faithful in keeping a split-screen mode, did away with not only split-screen, but system link as well with Armored Core V. Time will tell how this decision will pay off, but personally, I don’t like it.