Lyth would be my first choice oprner tbh. Still got no idea why he was jettisoned so quickly. He's a classy player.
Its difficult this one - Lyth is undoubtedly a class apart from Robson, Stoneman etc, and there is a very good argument that he was not really given much help to make it at the top level. On the other hand, he couldn't really complain at being dropped, and has never really beat the door down for a recall (unless you argue that he should be amongst the potential reserves for the much stronger one day side).
Looking at both arguments - the positives are clear - for three solid years he made runs for fun, and his Headingley ton against New Zealand was an innings that his Yorkshire teammates Root and Bairstow would struggle to match. He wasn't helped by management giving Trott three tests as an opener in the Windies which should have been a low key introduction to test cricket for Peanut, and he could legitimately say that in the live part of that Ashes series, he was always dismissed by a good nut, or in the pursuit of quick runs. You might even throw in the fact that he bowls functional offies, and is at worst third to Stokes and Rikki Clarke in terms of England qualified slippers.
The other side of the argument? Well, yes, he got six good balls - but only one of them was genuinely unplayable. The feeling existed then, as it does now, that he might unfortunately be a player who is good enough to nick good balls, but not genuinely great enough to get them to ground. That, you might let him away with - and rumour was, he was going to be given the winter after the Ashes - but for the fact that he patently cracked in the dead rubber at the Oval.