I: What if the group doesn't agree to using sociocracy?

It doesn’t (and shouldn’t) work to mandate sociocracy against someone’s will. Work with the people and assume that they tell you exactly what they are worried about. We know how that can be frustrating at times.

Try to understand the reasons for their not wanting sociocracy? What are their concerns? Can you relate to the concerns? How could they be integrated to make the governance system better/safer?

For example, maybe they are not objecting to sociocracy but to a way of implementation that seems too fast, or with not enough training, or not enough clarity of domains? Maybe they are objecting to an implementation where too few people have been heard, or too few people have been trained?

Our experience is that people might shy away from having to learn a new system (which makes sense) but soon get really excited about it. The most effective way to inspire them is to give them direct access to a first-hand experience, like an info session, a video, an appetizer process, or a talk. (That’s what we do a lot, and SoFA is comfortable as that “external” source.)

For more information, check out our handbook Many Voices One Song chapter 6

You don’t have to introduce sociocracy as a whole system, and often it is a disruptive idea to do that.
For two kinds of reasons - past and future reasons. Besides you can only do one thing at a time anyway. To decide about one whole system is stille one lot of things.
As for the past reasons, if the group has just some functionality already, remember “If it ain’t broke, don’t fix it.” instead look for where the dysfunctionalities are, where the pains, bottlenecks and frustrations are. Then propose to introduce a new method that will help with that. Sociocracy has something for almost all kinds of organisational problems, but it is not about sociocracy, it is about helping the organisation.
After you have lubricated the wheel, that squeals most, you have earned some credit and you can detect the next place that needs organisational help. … and so on.
Thus you get into the future, step by step - which you would have to do even if you decided to make a whole-system decision. Eventually you will have either an effective hybrid organisation or a whole-system consistent sociocracy.
The aim of the outlined process is (not to convert the organisation into a) sociocracy.
Sociocracy is a (lot of) means to the organisational ends and the purpose you already have. That is the baby - the resistance may be about a fear that you are about to throw it out with the bathwater.