This sounds cool! good luck with this research!

Some thoughts:

There are some ways to characterize different services, for example the Service Process Matrix (Schmenner, 1986), which looks at labor intensity and customer interaction, to come up with four different types.

I was also thinking about the 'application based' framework for classifying services, by Wynstra and Van der Valk, talking about 'component' services, amongst others. Those are types of services (purchased from service providers) that are transmitted/delivered directly to end customers. Hence, they form a component or module of the overall service offering of the buying firm.

You may also look into service triads (Wynstra, Spring, Schoenherr, 2015), which are these types of component services in a network of buyer-supplier-customer.

Specific work on service modularity by Chris Voss and others:

Brax, S. A., A. Bask, J. Hsuan, and C. Voss. 2017. Service modularity and architecture – an overview and research agenda. International Journal of Operations & Production Management 37 (6): IJOPM-03-2017-0191.

Voss, C. a., and J. Hsuan. 2009. Service Architecture and Modularity. Decision Sciences 40 (3): 541–69.

De Blok, C., B. Meijboom, K. Luijkx, J. Schols, and R. Schroeder. 2014. Interfaces in service modularity: A typology developed in modular health care provision. Journal of Operations Management 32 (4). Elsevier B.V.: 175–89.

Thank you so much Robert Suurmond for your suggestions. I have read most of the work by Chirs Voss and others, but I need to read other papers you have recommended. Once again thank you for taking time to reply my question. :)