TL;DR
Regardless of whether or not you use ROI or something else as a core metric, your real problem is that you need a way to measure the current and future value of communications. Measuring value often requires some a priori assumptions about the dimensions you will use to measure value, but once you have those dimensions you can generally assign a cost or potential return to them.
Estimating Current Communication Costs
As a thought experiment, consider some ways you might measure the current cost of your present communications:
- Time elapsed for "messages" (whatever that means to you) to initiate with a customer and filter down to the development team.
- Man-hours required to create, collate, approve, disseminate, or transmit information throughout the organization.
- Opportunity costs associated with missed or outdated communications.
- Labor costs associated with "idle hands" directly attributable to message cycle time.
This is by no means a thorough or canonical list. It's just some ways you might be able to attribute costs to the current communications processes.
Estimating Potential Value of New Processes
Once you have those numbers, you can then plug in the numbers for your proposed efficiencies. For example, you might say something like:
Currently, it takes 5 business days to solicit feedback about a feature from the customer. This cycle time represents a risk of US $237k in time, labor, and task-switching overhead in the event that the deliverable needs to be reworked or re-prioritized within the project. In comparison, a cycle time of 24 hours for feature approvals would result in an a risk profile of only US $7k, for a net risk reduction of US $230k.
This isn't the ROI calculation itself. Rather, it is a way to assign an estimated value of some sort to your proposed process. This estimate can then be used within your ROI calculations and projections.
Calculating ROI for Communications
Now that you have a set of costs and value estimates, you can estimate how much your business process change might cost to implement, and how long it might take to recoup those costs. For example using this calculation:
return on investment = (gain from investment - cost of investment) / cost of investment
would use your proposed cost-savings to determine if the investment in new communications processes and infrastructure would pay off within some acceptable time horizon.