So ... I've done triple decoctions and made some of my best. beers. ever. It may be that they received "care and feeding" that others did not, but I am a believer in this style of brewing. That and it's just plain cool.
I get where the OP is going. I think if a guy really
wanted to separate the needs of the mash proper from the needs of the cereal decoction proper, a standard step mash could be done (infusion or direct fired) and then the cereal cooked to get the rest of the characteristics from the decoction. Maybe. It doesn't sound that much "easier" to me though.
I would encourage someone who is entertaining undertaking this method of brewing (or at least achieving the "same" results) to actually do it once before looking for an alternative.