public abstract class BO<TConfig> where TConfig : BOConfigBase
{
    protected TConfig Config { get; set; }
    internal List<BC> _BCs { get; set; }

    public abstract void Init();

    public void Process() => _BCs.ForEach(bc => bc.Process());
}

public class BOOne : BO<BOConfigOne>
{
    public BOOne(BOConfigOne config)
    {
        Config = config;
    }

    public override void Init()
    {
        _BCs = new List<BC>()
        {
            BCA.Init(Config),
            BCB.Init(Config),
            BCC.Init(Config),
            BCOneA.Init(Config)
        };
    }
}

public abstract class BC
{
    protected BOConfigBase Config { get; set; }
    public abstract void Process();
}

public class BCA : BC
{
    private BCA()
    {
    }

    public static BCA Init(BOConfigBase config)
    {
        BCA ret = new BCA { Config = config };
        return ret;
    }

    public override void Process()
    {
        Config.Counter += 1;
    }
}