I can't think of a good way to do that. Do you have machines on the concourse? (not everyone likes machines). Or do you have staff? (that costs money). Perhaps you think it should be via an 'app' (Not everyone has a smart phone or portable internet device, or wants to/knows how to download the app).
The answer is all of the above. I like XC TMR, but the reason it has a weakness is that not everybody "gets" the obscure text message based system, and thus reservations are not offered fairly.
Consider a rethink:
- You buy a ticket at a TVM. When you do, the UI gives you a list of the next few likely connections with prices, DB-style, and you can choose to take a reservation at that point, and perhaps even select a seat if preferred.
- You buy a ticket at the ticket office. You are offered a reservation as you do so.
- You buy a ticket online near the time of departure. Same, you are offered a reservation.
And so on, and so forth. The final "walk up" feature would add the ability to insert a walk up ticket into a TVM (or present a ticket at the ticket office) and obtain one. Or use an app. Or text. Or whatever you want other than a horrible boarding scrum.
Then you have to get past those that don't have a reservation who are hanging about in the vestibules or aisles, and even then you have to hope no one decides to chance that you didn't show, or won't ask to sit in the reserved seat.
But you knew that before boarding, so you could choose to take another train if you felt that that was an issue for your journey. There are occasions when I would, there are occasions when I wouldn't. There are occasions when I'd upgrade to 1st.
Oh, and talking of 'no shows' who gets those seats? Do they remain empty?
One option is that the guard (we're talking IC here, there is always going to be an on board customer service member of staff, whether they have safety responsibilities or not) can go through and mark as available any unclaimed reserved seats. The other is that, just like now, you sit there (as you might sit in a reserved seat) and you might have to move.
It's basically a variant of the compulsory-reservation system operated by SNCF etc that doesn't outright bar you from joining an "oversold" train, but with many of the benefits.
Queuing area, hmm, isn't that just called "the concourse". Being serious for a moment, ISTR they used to have something like a queuing system at King's Cross, made it a pain in the rear to get across the concourse mind you, and didn't actually speed up boarding time or the scrum for seats.
It isn't supposed to be quicker, it may well even be slower. The point is that boarding scrums for uncertain seats (and that uncertainty may extend to whether reservations were placed or not, or whether the awful labelling system on Voyagers is even working today or not) is a stressful experience. easyJet realised, Ryanair realised. It's time for the railway to realise. In these days of higher loadings, it's really putting me off. My car, after all, never has this problem.
"The vulnerable"? Who exactly are they? The elderly, infirm and persons with disabilities can seek help from staff who should know which platform to go to and arrange a slightly earlier trip to the platform.
It would be interesting to know precisely how infirm you need to be to extract that information (other than gaming the system using RTT). But it's also difficult and stressful for families and the likes. Yes, they could reserve conventionally and stick to the booked train, but I think such a system allowing them to arrive at the station and reserve on the spot - and look at the seat map and say "there aren't 4 together, let's go for a meal and go back later" or something, would be a real customer benefit and is made very feasible by modern technology.