First off, if first-party is recognizably a problem, you would need a comprehensive action plan that revolves around both creation of content and realignment/structuring of resources to address that issue.
Also, what are the current SWOT picture of Xbox first-party, how does the budget allocation looks like in terms of first-party and what resources needed to be moved around and aligned to achieve that success.
First off, do a simple SWOT analysis. What are the current strengths/weaknesses of Xbox first-party. I think it's relatively simple. Solid studio structure that is conductive towards franchise management, ability for studios to manage SP/MP/GAAS components, internal collaboration with external studios for spin-offs and remasters/etc. Weakness would be difficulty to foster new internal studio IP due franchise studio setup, etc.
From there, derive the opportunities and threats. Opportunities would be to build areas of weaknesses, how to expand studios to a multi-studio structure, how to cultivate IP to be sustainable on annual or biannual at the same level as Forza, etc, how to monetize them over long term, and threats would be competition, internal politics, financial constraints, etc.
Upon deciding what are the key actions that need to take place, allocate the necessary resources to make it happen, and build sustainability plan and longevity considerations.