It is convenient that one can build forces from the MUL. (in the MUL?)
There doesn't appear to be any tool, produced, licensed, approved, nor elicit, that does formation validation.
Formation validation as defined in CamOps page 60 is what I am specifically referring to. Something that does custom units would be great but as yet I've seen nothing that does any validation.
The dream state would support two variations.
The first would allow the end user to define the formation type they would like to build and each unit added would lead to a calculation of validity. So building a Light Battle Lance, I add a FLE-19 Flea. This is a Striker and meets the requirement for being light but not for being a Scout so it can be included by I still owe the formation a Scout. Then I add an Awesome and I get told that Assault mechs don't qualify and so I remove it. Then I add a HNT-152 Hornet which is also a Striker. I still owe the lance a Scout which would be represented somewhere on the screen. I add a Locust LCT-1S, and I could see represented somewhere that I can add just about anything into that 4th slot as long as it is not an Assault.
The second variation of functionality would allow me to add 8-12 units into the formation builder and some magic happens and they get sorted into one or more valid formations.