You're not listening. You are risking breaking the law and if someone takes you to court, you will indeed 'put the organisation in a position that leaves it open to prosecution' if you break the law. Discriminating against someone, whether staff, volunteer or service user, because they have a protected characteristic, is against the law. You are mixing up the Equality Act with risk assessment and safeguarding.
'So we are in a scenario whereby there is supposed to be no hierarchy of protected characteristics, but there simply has to be for a number of reasons'.. No. That is against the law. There is no hierarchy of PCs, that is the law. You don't get to decide that a person with the PC of age outranks a person with the PC of religion, or whatever. You have to balance the equal rights of people with different PCs. It's non optional to do so. You absolutely have to make risk assessments, which are clear, unbiased and legally defensible, but you cannot discriminate against someone because of their PC.
I couldn't care less whether or not that is a material breach of EA2010 I really don't think you should admit that!
there is no legal compulsion whatsoever upon me to accept any and every volunteer who shows up No of course there isn't, no one is saying you have to take any volunteers who have a PC but who aren't suitable for the role; but there absolutely is a compulsion upon you to not refuse to employ someone (or give a service to someone) because of their PC. A CofE school can require all staff to be respectful of the schools Christian ethos; so they can refuse employment to a Muslim teacher who says they will be teaching the children that Islam is the one true faith. But they cannot refuse employment to a Muslim teacher just for being a Muslim. If you are doing the equivalent of that, you are breaking the law and no matter how good a reason you think you've got, you are risking being taken to court.
Genuinely, I think you are risking what you seek to avoid if you can say I will take the risk that I am in breach of the EA2010 where and when I believe it is absolutely necessary in order to pre-empt any possibility of a further, more damaging breach. It is not for you or any of us to decide to pick and mix what laws to obey, and if you do ,calling it safeguarding will not protect you from the potential 'bringing the org into disrepute, causing a legal shitstorm, losing our contract and losing the service for everyone' that you are trying to avoid. You cannot decide a breach of the EA is more or less damaging - the EA prevents discrimination, both direct and indirect, in the provision of goods and services. It doesn't prevent harm, that's risk assessment and safeguarding.