I have not used the XC 10 minute reservation system but have seen many posts complaining of the risk of being turfed out of ones seat halfway through a journey from a seat that was not initially reserved.
XC state the seats "may be reserved during this journey. Which means that, er, they might get reserved later. Its fairly simple stuff to grasp. An amber light would make it clearer again, I agree.
The trouble with XC is there aren't that many seats which are genuinely unreserved. Or not that many seats generally, for that matter. So if you don't have a reservation you have no choice but to hope the TMR system doesn't allocate your seat to someone else.
Another problem is allocating people on 8 quid advance long distance London tickets a seat, and others on £90 walk up anytime fares have to stand, as the train has become full before they boarded
As has been repeatedly explained, the advance ticket holders MUST be on that train whereas the flexible ticket holders can go get a coffee and catch the next train if they consider it too busy.
Few advance ticket holders arrive 2 minutes before departure because the consequences of missing the train are so expensive. So even if you went on first come first served, they'd still be in a seat before
A good system is to issue priority seat cards to those with disabilities and complex needs who require a priority seat. Which some TOCs now do. And leave the rest unreserved.
Fabulous if you're lucky enough to be fully able, travelling alone, travelling without baggage, and getting on at the origin station.
If none of those apply, well...
Who would qualify for a priority card? People with babies? People with children? People with large bags?
"I'm fit and I've got sharp elbows, so abolish reservations" is rather self-centred, don't you think? If having a seat is so important to you, bloody well reserve one.