The overall design of new IT Services is a delicate balancing act. The ITIL Service Designer must constantly be aware of shifting requirements (both functional and non-functional) as well as the need to meet carefully crafted performance targets.
There are three aspects of 'balanced design': Core Functionality, Resources and the Schedule a designer must adhere too.
(One further aspects of design - often overlooked - is the quality dimension. This is often stated as 'quality built in').