They pick them up and take them to their destination, like a taxi
More like an ambulance.

It's an emergency. RLNI and Ambulances only carry those in genuine need, otherwise..... get a taxi.
You've misunderstood. The skipper of the illegal immigrant's boat can be prosecuted for the offence of facilitation.
If they are acting within their job description, not stealing or being cruel, etc then it's the responsibility of the organisation, not the individual employed to carry out the task and function of that organisation.
When medical compensation, etc is awarded, it's the corporation that pays, not the individual involved.
So long as the individual is operating to carry out the function of the corporation/organisation, the individual's action are the responsibility of that organisation.
That requires evidence / witness statements confirming who was at the helm. a Volunteer SARs organisation cannot be expected to capture and preserve evidence.
What are you on about?
All the crew will know who was at the helm, who was in charge, etc.
Volunteer organisations will be as slick as any professional organisations, and will know who was in charge, who was at the helm, etc.
You suggested that Border Force sippers could be prosecuted.
I asked under what scenario could they be prosecuted?
And why would Border Force skippers be harder to recruit?