They can use data processing, detect anomalies better, leverage AI models, automate data extraction from analog records, ingest unstructured data like emails and memos, build complex financial dependency graphs, detect leaks, build custom scrapers, etc etc.
I'm sure there's at least one accountant in the loop, but you really want the team to consist mostly of data nerds.
You also seem confused; COBOL might be used, but it isn't the only tool available to accountants working for the government. COBOL is a straw-man. What you're describing here—software engineers who presumably have training in accounting—already exists, and they work inside and out of the government. This is an existing career path.
You're speaking about this as though you know a better way to do something, but it's already happening, and has been for years. Accountants aren't writing 62 year old programming languages waiting to die in their chairs while the world continues to progress without them.
Accounting just about anywhere you find it is already accomplished by accountants, some of them technically trained, as well as data scientists and software engineers. It's an interdisciplinary collaboration in any serious organization.