There is nothing "niche" about the high gain world. It is a huge market! (EDIT TO ADD: Sorry to pile on, I see someone already beat me to that a few posts earlier)
In these forums I am on the record stating that although I have no use for any high gain amps (JCM 800 is more than enough gain for me) I fully support you and others that want more options. If there are iconic high gain amps missing from the Helix, then you deserve to have them.
That said... if you think the Tweed Deluxe is a "clean amp"... then you obviously have a different take on what level of dirt quantifies as dirt. Very few buy a tweed deluxe for it's clean sound (volume lower than 3).... they push it into varying degrees of glorious overdrive.