I think the issue that I have with new penalty fare scheme is just the amount of time it will add to journeys. Normally one arrives about t minutes before the train, and you can normally visit the TVM (if It's on the right platform!) and then hop on the train. If there is a queue you can always abandon the TVM and get it from the guard/at the far end.
Now you have to allow for the possibility there MIGHT be a queue at the TVM and arrive, say, 10 minutes or so before the train, 15 if the TVM is inconveniently located (a la Steeton & Silsden) just to avoid the chance that you might not have got the ticket before the train arrives. Therefore there's a 5/10 minute penalty in excess journey time for every journey made, rather than just on the odd occasion when you had to queue at the destination to buy a ticket.
Given that journey time is one of the key competitive aspects against other modes, it seems a ridiculous handicap when we're trying to encourage modal shift away from private motor traffic. Not to mention the added inconvenience of potentially having to go to a distant platform to get a ticket and walk back, etc. It doesn't make rail any more attractive by making it more inconvenient, a longer journey tome and treating everyone as if they are out to stiff the railway.
Given that (as I recall) fare evasion is about 2% it seems a sledgehammer to crack a nut.
Maybe it is a sledgehammer approach, but given the scale of potential fare evasion something had to happen. On the lines concerned on the trial the timings between stops is often just a few minutes, meaning that on busy (often rammed at the peaks) 4 car units (soon to be 6 across 2 non-gangway units on some services) guards struggle to check tickets before the next stop. It was a frequent and depressing sight seeing numbers of passengers playing dodge the guard on almost every service I would catch, or running down to the far end of trains for one / two stop journeys, particularly before the barriers went in at places like Bradford Forster Square. So the one alternative would be to employ more RPIs, but then you might just end up with the same problem except at exits as opposed to entrances with queues forming to pay fares because the guard couldn't check all passengers.
The other alternative would be to ignore the problem and carry on as before, but as previously highlighted in this thread they have a franchise obligation to implement additional fare protection schemes. Just adding TVMs and hoping those passengers that regularly seek to avoid fares are somehow guilted into paying isn't going to work, so some kind of enforcement, or at least the threat of it has to be at least part of the solution. As for arrival times for passengers, yes clearly in some instances this will increase, I'm afraid that is a reality of the situation. We as passengers have the evaders to thank for that, in much the same way that airline passengers have the threat of terrorism to thank for longer queues at security and having to arrive in some cases 3 hours before departure. In order to try to enforce the requirement for all passengers to pay their way, some will be inconvenienced. Perhaps at certain stations Northern will have to review the number and locations of TVMs. Just because they are situated where they are now doesn't mean that they can't be moved or duplicated where the need arises. But frankly if you are travelling to Leeds or Bradford along the the Aire or Wharfe lines, an extra 5 or even 10 minutes time added to the start of your journey isn't going to make much of a difference when the alternative would still be more than double, treble, or even quadruple that by road.
For many evaders it will hopefully only take a few instances of being stung for £20 for a fare of a couple of quid to change their behaviour. Of course some will continue, but there are some that probably do it because it has just been too easy to avoid. And for the vast majority of honest passengers it can offer many to chance to pick up pre-bought tickets at their local station, where previously no opportunity existed. For others it may encourage more use of seasons, smart ticketing (just WY MCards at the moment, but eventually Northern plan to have their own) or M-ticketing solutions, which in the long run help in some small way to reduce costs. The bus operators are rapidly working on new e-solutions, so now is the time for TOCs to also make improvements. For those that do not wish to use online ticketing, they still have the chance to buy either at a TVM or pay onboard with a Promise To Pay (which from what I can see is more or less one click on the screen).
But whatever they did not everyone would be happy about it, you can never design any system that will be to the full satisfaction of all users. All companies like Northern can do is to try and balance the needs of passengers, convenience and revenue protection. Whether or not this is the right way forward remains to be seen, if they get it badly wrong and it causes chaos I will happily admit I was wrong for cautiously supporting it. All I can say at this point is that I see no real changes save the guards selling a few less tickets onboard. Of course that is entirely anecdotal but for me at least not surprising.