What is the aim of this indicator? Is it for evaluating the success of the transformation or for assessing the maturity of the concerned system in terms of a particular technology use?

I think you can use the part of Process with the use of Artificial Intelligence or Machine Learning technologies.

Whilst this is not a direct answer - you may want to read some of Gordon's work on the impact of ICT versus the impact of the other "General Purpose Technologies" and the installation/learning and exploitation phases of adoption of technology. It may drive a way of finding an indicator. Bryjollfsson's work may also help out on the ICT side as well.

Gordon, R. J., 2000, Does the" new economy" measure up to the great inventions of the past?, Journal of economic perspectives, 14(4), 49-74.

Gordon, R. J., 2004, Why was Europe left at the station when America's productivity locomotive departed?, (No. w10661). National Bureau of Economic Research.

Gordon, R. J., 2012, Is US economic growth over? Faltering innovation confronts the six headwinds, (No. w18315), National Bureau of Economic Research.

Gordon, R. J., 2013, US productivity Growth: The Slowdown has returned after a temporary revival, International Productivity Monitor, (25), 13.

Gordon, R. J., 2018, Declining American economic growth despite ongoing innovation, Explorations in Economic History, 69(C), 1-12.

Brynjolfsson, E., & Hitt, L. M., 1998. Beyond the productivity paradox: Computers are the catalyst for bigger changes. Communications of the ACM, 41(8), 49.

Brynjolfsson, E., Hitt, L. M., & Yang, S., 2002, Intangible assets: Computers and organizational capital, Brookings papers on economic activity, 2002(1), 137-181.

Brynjolfsson, E., & Hitt, L. M., 2003, Computing productivity: Firm-level evidence, Review of economics and statistics, 85(4), 793-808.

Brynjolfsson, E., McAfee, A., Sorell, M., & Zhu, F., 2008, Scale without mass: business process replication and industry dynamics, Harvard Business School Technology & Operations Mgt. Unit Research Paper, (07-016).

Brynjolfsson, E., 2011, ICT, innovation, and the e-economy, European Investment Bank, EIB Papers, Luxembourg, Vol. 16, Issue 2, pages 60-76.

Brynjolfsson, E., & Mitchell, T., 2017, Profound change is coming, but roles for humans remain, Science, 358(6370), 1530-1534.

Brynjolfsson, E., Rock, D., and Syverson, C., 2017, Artificial Intelligence and the Modern Productivity Paradox: A Clash of Expectations and Statistics, National Bureau of Economic Research, NBER Working Paper Series, Paper No. 24001, November 2017.