This thread should be referenced henceforth whenever a suggestion for movable solids is made.
I am going to break down almost every reason why they should not be requested. In order to code movable solids, one must code them in such a way that each particle attaches itself to another. Simple enough, right? However, if that's all you do, then any particle would "connect" to any other particle it touched.
Now, for movable solids to do what you want it to, you have to code it so that only particles of the same element "connect." Again, seems simple. However, in real life, when a piece of metal is dropped onto another piece of metal, they would "clang" and the first piece would bounce away.
If you only code it so that METL connects to METL, then dropping a piece of METL onto another would just connect them. So, you would also have to code solids so that TPT could recognize whether or not the METL particles were placed together, or had collided after the simulation had started.
Assuming you could code that, well now you have to code rotation. A developer would have to find a way to code solids to recognize the angle it strikes, and have each particle move along the x and y axis accordingly, while still falling according to gravity's pull.
On top of all of this, there are even more issues I'm not going to go into. So, if you want movable solids, either wait until someone somehow develops the code, code it yourself, or go play dan-ball.
i have to show you something in my mod. it has a sort of moving solid that works pretty well when you do it right. pdmd will turn into a moving solid if you click just right.
EDIT: Hmm.. it APPEARS to be a moving solid, however it's simply powder falling at the same velocity. Because it's so heavy, and the diffusion is so low, it looks like a solid when it's really just powder falling straight down.