It does not say merely, "a site that is convenient for living," but "that is convenient for the observance proper to your order." Not all places and ministries are suitable to the contemplative and austere characteristics of the Rule. The primary concern, as I read this text, is not to accept a site wherever it has been given, but those where we are able to maintain our identity and the Way of life prescribed by the Rule itself. The site must be suitable for Carmelite life, that is, it should not be in a 'wilderness' area that constantly fights against our Way of living, or forces us to adapt, or abandon the values central to our Carmelite identity. What these values may be is a question for deep discussion, but that they should be protected is not. The Rule clearly tells us to be discerning in where we accept houses and establish communities not according to the needs of a particular area, or to the Church, nor to what is convenient for a lifestyle that we may have become accustomed to, but the primary factor that is raised above all others, is the effect of the ministry and area on our ability to live our Way of life.
Is this a question that we ask when considering invitations to new ministries? Are the demands of the life of a parish pastor, or high school president/principle compatible with the communal and contemplative life of a Carmelite friar? Are full-time salaried positions with modern benefits compatible with a life of poverty that renounces ownership? Are large cities convenient for a life of simplicity and solitude?
It seems to me that there are no strict answers which apply to every situation, and that there is a reason why God moved the Carmelite way of life from the desert wadi into the landscape of cities and rural populations, but perhaps the Rule is telling us to be more courageous in passing on what may appear to be immediate needs of the Church, to give our first attention to the "observance proper to (our) order," and then allow our brothers to engage in ministries so long as they do not interfere our first obligations.