Multi-objective, multi-period location-routing model

I am in need of an expert in operations research and mathematical modeling who can develop a multi-objective, multi-period location-routing model, based on several critical assumptions like heterogeneous vehicle and differents types of products.

Ideal Skills:
- Proficiency in developing complex models for multi-objective optimization.
- Strong understanding of both location and routing optimization.
- Proficiency in GAMS programming.

For this task, I expect the following deliverables:

1. Review the proposed model and adjust the formulation as needed to ensure valid results.
2. Refine the mathematical model in GAMS and validate it using test instances in Excel.
3. Implement the multi-objective weighting method to solve the problem and assess the relative importance of the objective functions.