This hospital design article explores what it means to design in flexibility, especially regarding cost and time trade-offs. There is a nice discussion of acuity adaptable rooms:

The discussion of flexibility in
design and time is really explored as the research of acuity-adaptable
and universal rooms is further developed. This subject has been debated
for the past 15 years and can be very misunderstood.

On one end of the spectrum is the idea of room size standardization.
In this case, the inpatient room size and configuration meets all
requirements for critical care. [In other words, designing rooms that can be converted back and forth between med/surg and critical care beds as needs dictate.] The design team must explore the
extent to which this idea should be incorporated into planning the
entire facility, or just a portion of the inpatient units.

On the other end of the spectrum is the concept of an inpatient unit
in which each room is designed, planned and equipped for the most
critical patient and the patient therefore remains in the same room
throughout his or her entire stay. Thus, the staffing changes to match
the patient needs and to conform to the required staffing ratio. This
introduces a significant operational impact that has stirred great
discussion. While not applicable to all rooms or units, the concept has
the opportunity for great improvement in operational efficiencies,
reduction in medical errors, infection control and patient privacy.

Given the small numbers of patients that actually meet critical care unit admissions criteria, I don't know that variable acuity rooms must flex all the way up to "the most critical" care level. Many hospitals are supporting monitored patients and patients on vents with little or no remodeling. Most new hospitals should be designed to only flex up to telemetry or high dependency units - just short of ICU-level acuity.