Gr8 idea Rich. In that case, another cable is a must for audio. And TV manufactures should assure about lossy and lossless audio including object based audio pass through by HDMI 1.4 ( in HDMI 2.1 by default we can get it).
If HDMI 1.4 promise us lossless audio and object based audio even in bit streams, it will definitely replace optical/coaxial SPDIF outputs everywhere.
I agree that eARC will require new everything. But don't we see the market, how quick it jumped DD and DTS to TrueHD an MasterAudio, and all the way to Dolby Atmos and DTS:X. And how quick it moved to HDMI 2.0b from HDMI 1.4. And year by year the change in tech has been very rapid.
If we see 2015 AVRs we had only HDMI 1.4 and No HDCP 2.2 and was no HDR Support. And by 2016, we got HDMI 2.0, 2.0a and even 2.0b version with HDR and HDCP 2.2. One year back so many people bought high end AVRs and Pre Processors that support only Dolby Atmos but not DTS:X at any cost.
But now DTS:X is seen everywhere along with Dolby Atmos.
Now my point is, It won't take much time for market and users to adopt HDMI 2.1 It simplifies the things.
I would want all future TVs and AVRs/PreProcessors and Blu-ray palyers from now on-wards, from the right minute on-wards, provide HDMI 2.1 ports with all its features enabled.
And I agree with you that there were so many problems/ issues about HDMI connectivity and ARC feature.
But I strongly hope all those will be resolved and communication between devices would be so smooth with HDMI 2.1.
The idea of yours is so cool too, to have 'HDMI 1.4 audio only out' just like the way few high end blu-ray players do have. But hello TV Manufacturers - are you listening to real time user opnions ??