Guidance Needed from Blueprint Experts on Mitigating Key Risks in Existing Pega Application

Hi Experts,
Looking for guidance from the Blueprint community on addressing key risks identified in a client’s existing Pega application before accepting further development or starting new sprints.

Key challenges observed:

Heavy use of long lived branches in QA/Prod (200+ rules per branch), complex Activities (60+ steps), and instability when branches are removed.
High technical debt: Guardrail score ~71% in Prod with ~10K warnings; extensive use of deprecated rules.
QA and Prod branch/rule misalignment leading to deployment and testing risks.
Upgrade constraints: Pega v8.8 with UIkit v7.7

Ask:
From a Blueprint best practice standpoint:

Should stabilization/remediation be mandated before new development?
How would you sequence branch rationalization, guardrail cleanup, UI modernization, and platform upgrade?
Any proven patterns, artefacts, or assessment approaches to position these risks with business stakeholders?

Appreciate any insights or experiences. Thanks!