So, I'm playing an Artificer themed Alchemist, and this fun idea brewed in my head.
The Imp Familiar is in Bestiary 3, p229, the Rakshasa, Raktavarna.
It stays in the form of any object, and can become any weapon, using the Tumour Familiar as the base, this means I'd be able to pull out any weapon out of my body. Proficency is an issue as an alchemist, which is where Intelligent Item comes, adding the Proficient Ability, making it possible to change weapon at will.
The other reason is, so it can be enhanced normally as well.
Default it's a creature, but stays all the time in object form. So it's not that different. Fluffwise, it could be another creature than Rakshasa, Raktavarna, it could be a homunculus of sorts.
I'd say something similar to amulet of might fists would do the trick, leather strapping and a brooch-like seal wrapped around the weapons handle for instance, likewise Magic Fang could also be used.
If you have a construct enhancing it should cost you extra since you are essentially giving it an improved transformative ability, it's a GMs call though a little leeway for flavor doesn't usually hurt the game.
Think it could balance out by removing the Spell-like Abilities, and then counting it as a Intelligent Item for effects and purposes of spells and crafting?
The reason I can't just get a transformative intelligent weapon is because as a tumor familiar, it can reside inside me as well as heal itself up fast this way, meaning I'll always stay armed.
Not to mention that intelligent weapons have some interesting abilities, such as Leaping and Proficient.