More food for thought -

Might want to look at how Princess Stomper handled the "LN_Sittin" (and kneelpray/standpray) animations in her "Ald Redaynia Extended" mod.
Could give you some ideas.

DARoot

Some more thoughts to try to help:

Consider having a look at the MCA_Courtesan scripts used in "Morrowind Comes Alive" and the scripts used in "Mr. Cellophane's Lovers and Legends" (MCA and LAL, for short) for how these scripts position the Player for,..erm... what the scripts intend. (Sorry, no links. This is a family forum).
Both use activators (in MCA, they are placed on certain beds in the Construction Set beforehand. In LAL, it's a miscellaneous item (a rose) that the Player can carry, and can place where desired in-game. LAL requires MWSE, but you may not need that for what you are trying to do). Anyway, rather than making a "carryable chair," you could use a small object (e.g., a ring) that carries your script, the script once activated places the Player relative to that item (not the furniture), and then the Player could (in theory) place it ANYWHERE in-game, and be able to "sit down" on ANY existing (vanilla MW or custom mesh) chair, bench, bed, rock, wall, defeated enemy, etc. that has its own inherent collision.

Hope this is helpful, and that your creative juices are flowing.