Frostcrag Spire has an alchemy table, and in the Shivering Isles dark smith's shop there are some bellows and a hearth. Perhaps you can use the existing models scripted with your effects?
Perhaps, but I'm just not motivated to start learning how to edit interiors. If someone else can do this, then I have the idea of how to do the needed scripting though.
But until then, I guess I give full benefits if alchemy and repair is performed while in a cell owned by the player, and full penalties if in a cell not owned by the player/his factions - and leave the rest to imagination. One advantage of this approach is that it will automatically work for all mod-added houses, as long as they set the ownership correctly.
I like your mathematical configurations. Repair sounds just right, especially with the new "effectiveness" variable.
Alchemy sounds good, too. Although, I do still think it would be really neat if the higher level potions were not available in the field. It just makes sense in my head, feels right, for something like a potion of invisibility to require some peace and quiet and specialized equipment - sort of like a lab.
Yes, I think getting to see one effect less (minimum one) outside makes sense. I'll see if it will work without making the alchemy equipment unusable at the same time.