Archbishop Vincent Nichols seems to have come out in favor of civil unions, while supporting Church teaching against homosexual marriage. (Really?)
We would want to emphasise that civil partnerships actually provide a structure in which people of the same sex who want a lifelong relationship [and] a lifelong partnership can find their place and protection and legal provision… As a Church we are very committed to the notion of equality so that people are treated the same across all the activities of life. The Church holds great store by the value of commitment in relationships and undertakings that people give… - Source
In a post titled, Archbishop Backs Equality, Fr. Blake pointed out, "He did go on to say, 'equality and commitment do not amount to marriage'".
My first impression is that the Archbishop's reasoning sounds suspiciously derived from the pastoral notion that a monogamous relationship between two consenting gay adults is better than living a promiscuous life with multiple partners. It is a very permissive proposition...
That said, even if the Church were to approve civil unions - which a few other bishops have also stated that they would not oppose - it will not be enough for gay activists. Eventually - like concurrently - they will seek some sort of blessing, some sort of commitment ceremony, probably claiming Boswell's medieval studies which pretend to site precedence, and so on. Inevitably, 'equality' as Nichols esteems it, will sooner or later require recognition of same sex marriage - and acceptance of same-sex adoption. 'Equality' has become a doublespeak term - with or without the 'marriage' qualifier.
In my opinion, there is no compromise to be had that will not end in contradicting Catholic Church teaching.
BTW - Non-married couples, straight or gay have for years arranged matters legally in order to take care of their friend-companion-partner after one of them dies. Marriage or civil union contracts are not necessary.
More fallout here.