Hello.
Side by side versioning with biztalk is doable but difficult.
In your case, I would look at using direct binding. If you need side by side versions of your schema you need to make sure you include the schema assembly version or another custom set property that can be used for your subscriptions inside the Orchestration.
You need to make sure if you version your schema you can not use the default Xml Disassembler or Assembler.
Basically, you need to think of side by side versioning as really a full, new solution you want to deploy.
Hope this helps.