If Nikki and Carmella can get a gimmick match for a title-less feud why can't the actual title feud get one? There's still time for a stipulation to be added, a TLC match would be too excessive, a ladder match could go very wrong...what about a cage? I digress. I think Bliss is going to become the second ever SDLive Women's champion come TLC.
They will likely make it a tables match. The usual set up for TLC is a Chairs, a Tables, a Ladder and a TLC match and they've filled every role except Table. If they gimmick the tables to break with less weight I don't see how it could go wrong, its less risky than a ladder or TLC match while also being a step forward for the division.
I don't understand your comment on Becky Lynch having little reaction and Alexa gaining popularity, I don't think we're watching the same show Solidus. Becky Lynch's reign has been underwhelming mainly due to her being sidelined with a medical issue, their match on Smackdown was great (Though I would say a big chunk was cut for commercials on TV as opposed to being in attendance like me). I see Alexa Bliss gaining popularity online sure but she's always been popular because to the IWC any female who is attractive is popular, not to diminish Alexa Bliss as she's good in ring and a great promo but in terms of crowd reactions its very much in favour of Becky Lynch with Alexa getting booed which is exactly what you would want.
People underestimate how popular Becky Lynch actually is, even online. /r/SC is a freaking mine field when it comes to her (Example: Bryan Alvarez said that Kevin Dunn didn't like her accent and /r/SC turned this into Dunn is taking the belt from her and cutting her TV/Promo time so he is public enemy No. 1 over there.) and Twitter she has her die hard fans but when it comes to even crowd reactions she definitely gets the best on the Smackdown Live Women's roster, I'd say she's on par with Sasha banks for reactions which is a positive.
I'd go with Lynch winning this one as I don't see them making her drop the title with no clean defences but thinking Alexa will win clean is probably the least likely outcome. The best case scenario would be a Tables match with Lynch winning where this gives Lynch her title defence but also protects Alexa for a future title feud, the SDL Womens division is too bare for them to make Alexa or Becky lose clean tapout or pinfall.