I’ve gone 'round on this in another thread. While there may be no formal “vow renewal” ceremony in the Book of Blessings (I’m not 100% sure of that actually), neither do I see vow renewals as a problem. Re-exchanging the marital vows in the context of the blessing seems to me like a beautiful and meaningful thing.
Clearly marital vows don’t “need” renewal in that sense. On the other hand, regarding Baptism, which is a once-in-a-lifetime sacrament which imparts an indelible character on the soul, the Church provides several opportunities to literally renew our Baptismal promises: at the Easter Vigil and at Baptisms are two such instances. Marriage doesn’t impart such an indelible character, and to my way of thinking, if we can renew our Baptismal promises, it seems incompletely thought through to say that marital promises can’t / shouldn’t be renewed as well. In an era when traditional marriage is under attack and so many Catholic marriages end in divorce, I think the Church should do everything possible to recognize, support, and bless long-term marriages. But that’s just me.
As to whether or not an “outside” renewal is possible, I’d think that would be up to the officiating priest or deacon. Since it is not a sacramental action, the rules of being in church don’t apply. Blessings are imparted outdoors all the time. Even under the old Roman Ritual, there are lots of blessings that can ONLY be imparted outdoors: blessings of boats, of fields, crops, animals, locomotives. There’s even an old Roman Ritual blessing of beer, but that’s surely another discussion.