I think the current strategy is very much focussed on city based...

I think the current strategy is very much focussed on city based biogas, as these are often sited in industrial areas, close to markets, will likely be carbon negative, have great green credentials and attract grants and fiscal incentives. They will also be well supported by green groups, who will be less supportive of natural gas. This strategy has allowed Hazer to get on with business with good support and few obstacles as they demonstrate commercial production.

But in the end, I expect the strategy will be customer driven based on feedstock resource size and location. So small to large biogas producers to potentially very lare scale natural gas producers. For the large scale natural gas feedstock, the optimum would be a facility near an existing production area or pipeline, ideally near a port for export.

So in my view the answer to your question is that there will likely be a large range of both project sizes and business models deployed.

There's really no limit in this sense. For example, you don't have to be a gas producer to deploy the process. You just need access to gas, so you can be a gas buyer and project developer.