Form comes from wonder. Wonder stems from our 'in touchness' with how we were made. One senses that nature records the process of what it makes, so that in what it makes there is also the records of how it was made. In touch with this record we are in wonder. This wonder gives rise to knowledge. But knowledge is related to other knowledge and this relation gives a sense of order, a sense of how they inter-relate in a harmony that makes all things exist. From knowledge to sense of order we then wink at wonder and say How am I doing, wonder?
Whilst Feature Parity often sounds like a reasonable proposition, we have learnt the hard way that people greatly underestimate the effort required, and thus misjudge the choice between this and the other alternatives. For example even just defining the 'as is' scope can be a huge effort, especially for legacy systems that have become core to the business.
Most legacy systems have 'bloated' over time, with many features unused by users (50% according to a 2014 Standish Group report) as new features have been added without the old ones being removed. Workarounds for past bugs and limitations have become 'must have' requirements for current business processes, with the way users work defined as much by the limitations of legacy as anything else. Rebuilding these features is not only waste it also represents a missed opportunity to build what is actually needed today. These systems were often defined 10 or 20 years ago within the constraints of previous generations of technology, it very rarely makes sense to replicate them 'as is'.