I think the identity of the ST is wrapped up in the idea that it is the best sounding floor standing speaker under $2000. The further you deviate from this, the less sense it makes to retain the ST branding. The Supercharged ST already deviates quite a bit. Going even further may not make good sense. If the bass performance of this new speaker is very similar to the HT2-TL, then I would place this speaker in the Veracity line as a few others have suggested (since the midrange and top end will also be very very similar). I think it may have also made better sense to place the SCST in the Veracity series since it is probably more similar to the HT2-TL than the standard ST. But I suppose re-naming is not an option now.
As far as naming, I would leave ST out entirely and go with some version of HT2-TL(x). Maybe (c) for compact or something similar, but equally simple. Or maybe add the driver size in parentheses and add this to the other models too, including the HT2, HT1-TL, etc.
Just my thoughts...