How to: One pipeline's success; In separate repo modify config and push and kick off pipeline

Desired Outcome:
Update Repo B config after the successful deployment of RepoA

What ideas do people have for achieving automatic code changes and subsequent MR/Acceptance/Merge to Master on a given RepoB when RepoA completes deployment of npm/module or .jar?

While we could use something like some-npm-module: latest but that would get out sync as RepoA/RepoB are promoted through higher environments,

My current idea
I’d like to treat the automated pipeline like any other developer
RepoA has a step that opens an MR with the latest package-tag in RepoB, approves, and merges it to RepoB.
Does :arrow_double_up: seem feasible with GitLab API?