Hopefully, I understand what you are trying to do. I agree that linear bass response should be the goal. But, I think I disagree with your assumptions and how best to achieve that.
Unlike you, I firmly believe in hi/low pass xovers for bass management and sub integration. I do not believe in sending bass signal to a speaker below its rolloff comfort range where it might distort, or draw excessive power from its amp, even combined with the sub output. In other words, I believe one key advantage of a subwoofer is that it creates a biamped situation by offloading all deep bass duties to the subwoofer and its amp, or multiple subs. Eliminating the hi pass filter and running the main channels full range defeats that.
My approach is similar to what all HT AVRs and prepros do "out of the box", though they sometimes may offer a secondary option closer to yours, with main fronts run full range. My old prepro called this option "double bass", but I was never happy with that. I do not think I agree with your analysis of the negative consequences of simply transferring all frequencies below the crossover point to the sub channel combined with any .1 LFE content from the source medium, which normal bass management does automatically.
I no longer use a prepro. JRiver, in addition to everything else it does, performs most prepro functions for me, including bass management. The media I listen to are music and video in 2.0, 3.0, 5.0, 5.1 and 7.1 sound. For bass management, I have simply used Room Correction to set channel by channel hi/lo pass xovers as appropriate above the response rolloff points for each speaker channel per measurements. And, to do that, the JRSS mixer setting is Silent. It works perfectly and it sounds great.
Incidentally, I use Dirac Live for DSP correction, not PEQ. I also use Zoneswitch, but all my zones contain the same bass management parameters in Room Correction.