Can you benefit from Bladesong while Shapechanged into a Marilith?

Shapechange allows you retain your Intelligence & class features, while taking up your new forms’ physical stats. In theory, this means that a Bladesinger could change into a Marilith and get 7 attacks with crazy modifiers using Bladesong, while having really high AC and Concentration saves.

However, a few questions came up:

  1. Swords Not Included™: You would need to supply 6 melee weapons rapiers to benefit get the most out of Song of Victory. How could you effectively carry these before Shapechanging, and effectively wield them afterwards?
  2. Assuming this goes smoothly, would your weapon attacks be at +11 to hit (+5 Dex due to finesse + 6 proficiency), or the Marilith’s +9 (which appears to be +4 from Str, due to longswords not having finesse, and +5 prof)?
  3. Would the damage be 6d8 + 60 for the sword attacks (w/ Song of Victory), plus 2d4 + 9 for the tail?
  4. Would AC be 18 + 5 (Bladesong) = 23 (+5 optionally with Shield) ; and +15 Concentration Saves?

Granted, it’s no Wish, but vs a handful of powerful targets (especially with Spellcasting), I feel like it could really bring enemies down quickly and hold the line, ideally if Hasted by a party member.