Okay, I have a friend who is interested in playing a merfolk. Rather than tell her about how bad tails are for dungeon crawling, I've opted to resurrect and idea I had before: a merfolk who change change her fins to feet and back. (A moderately common notion for merfolk). Problem is, I don't know what to do about some complications that arise from that kind of change: everytime she shifts, what would happen to the clothes and armor she wears below her waist. Right now, I have some ideas, but I want some feedback.
1.) Everything below her waist merges magically into her tail and back again: akin to a druid's shapechanging. Its non-functional, but when she returns to human form, she still has it.
2.) Same as above, but doesn't apply to her feet: she can't wear boots/shoes and shapeshift without ruining them.
3.) Everything below her waist automatically falls off on the ground. Any armor worn on her legs, boots or shoes, and pants ends up on a pile on the floor. Its probably more "realistic" than trying to explain how her gear merges into her, but everytime she shifts back; she's naked from the waist down. (I suppose a robe or dress would still work though).
4.) As 3, but unless she takes the time to take off said items, they could be ruined. (Clothes ripped, buckles break, shoes tatter). Most "realistic" type of transformation, but least "fun".
So I'm looking for some advice on how to handle this transformation in the most logical (yet fair) way.