I think you’re trying to solve a nonexistent problem in terms of RPIs allegedly stealing tickets, but you do you.
It's the same in all walks of life. If you had a ticket (which didn't have your name on it) to a football match and someone stood outside the ground, away from the turnstile, wearing a hi-viz jacket asked you to hand over your ticket, would you hand it over?
I'm sure that the vast majority of RPI's are fine but unfortunately for that job role, there are a few who do it for the power trip and enjoying making people feel small. At the end of the day, RPI's are there for Revenue Protection and that means ensuring people are travelling with a valid ticket. If I can prove this by SHOWING them my ticket, I see no reason why it would need to go any further and that is exactly what my experience has been - I've never experienced a RPI demanding that I hand over my ticket and the reason I have never experienced it is because all the RPI's I have come across have the sense to see that me showing them a valid ticket is all that is required for them to have completed their job role!
What about an RPI on board the train?
My experience of this has primarily been on Merseyrail where they literally take a fleeting glance at the ticket and move on without needing to fondle it!
However, should I come across a RPI who is demanding a feel of my ticket, I'd maybe request that they call the TM so I at least have a railway staff member witness the interaction. I imagine the less scrupulous RPI's would be less willing to head down the power trip route with another railway staff member present and might realise the utterly pointless request to hold my ticket has cost them a lot more time than a quick glance at my ticket would have taken
Your ticket has to be handed over for validation and where appropriate, clipping/stamping, it is very much the norm in most places for tickets to be stamped or marked.
All can be done whilst I retain possession of the ticket. However, I have already said that I have no issue with an onboard TM clipping/stamping my ticket for validation
If I refuse to show an inspector a paper ticket do they get to search me to try and find the ticket or get ID such as a driving license?
Don't get me wrong, if I am unable to present a valid ticket when asked or refuse to produce ID then I should be put through the process and my refusal to comply recorded, but if an inspector wishes to take matters further they should involve the BTP.
I'm not sure of the rules and laws for searches but I presume they could get BTP involved who I guess have some sort of stop and search powers. However, they are more likely to simply hit you with a penalty fare or take your details for further investigation and potential criminal proceedings.
I now SussexSeagull hasn't specifically responded to any of my posts here but just for avoidance of doubt none of what I have said in this thread relates to a refusal to show a valid ticket and it would never make any sense to head down this route if you have a ticket