Successful synthesis of a new design requires balancing of trade-offs that arise from multiple competing design objectives and constraints. Early-stage design synthesis typically does not consider detailed technical constraints; a task left to late-stage mathematical design optimisation to refine an already-determined configuration. The recently developed Multi-Objective Monotonicity Analysis (MOMA) has shown that design optimisation can be used successfully in configuration redesign. This article extends the MOMA approach to early-stage design. Synthesis of an aptly named ideal design is achieved by focusing on the avoidance or reduction of trade-offs and by managing active constraints across all stages of the design process. The ideal design meets a set of formal conditions, which provide the basis for a systematic collection of corresponding design principles that can be selectively combined to create new embodiments, avoiding overly restrictive trade-offs and constraints. These principles are consistent with the decision making of experienced mechanical designers, shown here in the industrial practice for designing drug delivery devices.