Perhaps time to market.  Automakers always strive to cut the time from idea, to prototype, to market

I would add the following independent variables:

• Flexibility of the supply chain (process perspective)
• Degree of organizational learning that takes place (learning and growth perspective).
• Human resources (various possible proxies)
• Cost effectiveness (financial perspective)
• Customer satisfaction (customer perspective)
• Technology and innovation
• Information management / IT
• ...

Firstly, u need to define the set of customer needs a firm seeks to satisfy through its products and services. Then only u strategize the product development strategy, specifies the portfolio of new products that the company will try to develop. In this case the automotive models in the industry and market. Marketing and sales strategy specifies how the market will be segmented and product positioned, priced, and promoted. Need to be reminded, supply chain strategy determines the nature of material procurement, transportation of materials, manufacture of product or creation of service and distribution of product. All functional strategies must support one another and the competitive strategy. Hope these will clear some points before u started to design ur theoretical framework into the dependent variables. Cheers.