All of the other characters either throw the enemy away, move themselves, or have considerable lag after a back slam. Fast rising enemies will get away and make you have to reposition if you can repeat the back grab at all; not even close to the same thing.
Which characters exactly are you talking about? I tested the moves I mentioned before over the course of a few minutes before I made that post, so I know all of them work just fine against a wall using the method you described in Mania, moving neither themselves nor the enemy away,and those characters can get wall regrabs setup pretty easily with a jumpkick if need be. I'm not sure who you're referring to that has so much lag after a slam that they can't regrab an enemy against a wall as I've tested this with almost all the characters. His invulnerability frames end and he can move as the enemy starts to recover, but you have plenty of time to regrab for a suplex when the enemy's been jumpkicked against a wall. The only enemy who I can think of might give someone trouble is SoR3 Donovan who recovers absurdly fast and even Adam, who's rather slow, can regrab him after a suplex without any issues. They're encountered with walls around so rarely that it becomes a moot point, and not much recovers faster than they do.
Most of the 2/3 star blitz attacks have too much lag and leave you wide open.
If all of the enemies are up against the wall, any slight ending lag on a 3-star move is irrelevant as you'll recover in time to use it again. Obviously there's some risk involved if you're using it against a wall without all the enemies trapped, but even if a new enemy shows up from behind the damage potential on the crazy strong blitzes generally makes it pay off, especially in lower difficulties with less aggressive enemies.
On top of all that, you are somewhat safe since the backdrop will knock other punks away. Again, the faster your victim gets up, the safer you are.
Forgot to address this earlier point; the safety of having Blaze repeatedly suplex someone against a wall is quite debatable, especially on higher difficulties where enemies aggressively take advantage of openings. I don't see relying on this as being very safe with a lot of other enemies around as the suplex doesn't have that much range for hitting other enemies, and there's a couple seconds Blaze has to wait before she can regrab most enemies. Call me skeptical, but I don't see how this works as well as you say on the SoR2 route's stage 7 elevator among groups of such aggressive enemies who will easily hit you in between suplexes (the kickboxers in particular love rushing up to knee you, even after a throw) unless you're taking about using this method of attack when there's only one ninja or kickboxer left.