I'm not sure I understand the reasoning behind this. You can have all states in one workflow and have conditions set up to control files during transition. Why make up multiple workflows unless they are different processes.
Our vault was initially setup with pretty much all files on their own workflows. I was considering it as an alternative, since most of the workflows have a set if common states (i.e. some skip checking, other have approval from another dept.). I was also trying to avoid a monstrous workflow with transitions all over and crossing.
I might be able to do a combination of the two ideas, separate out the bulk of the common bits into one workflow with links to alternate workflow transitions as required.
Generally, you would want a workflow for a process. Sometimes the process is so large and has smaller sub processes that it makes sense to make separate workflows. Yes, you can have conditions to control your files to go to certain workflows. I use conditions for this and base it on location and type of file mostly. I usually don't have any issues with this. You definitely need to thoroughly test out each workflow to make sure it works correctly in the different folders and with different file types.
I do not understand your main reasoning behind this kind of approach.
You should be able to get everything done using rights both States and Transitions.
Having too many workflows creates problems in Documenting your Vault Setup(If thats something you see yourself doing).
Also while reporting you want to have all the states in a group (Workflow).
I generally like to send files from between workflows only if there is an approval process (A complex one) and I dont want to recreate everything(States ,Transitions,Rights,Dispatch or any other customization) again.