Can't understand the overseas situation. Have we been massively unlucky? Maxwell was/is one of the worlds leading white ball cricketers, was so clearly the best available player to us at the time. Did we expect too much? Was he as bad as we remember? I'm not sure he was. Was fair to expect more though.
Re. Worrall. Hold on a sec, he played for Gloucestershire for 3 or 4 seasons so it's not like Surrey unearthed a gem out of nowhere. Only when he gained his British passport did Surrey pinch him. Good player though, clearly.
Jeets what a player, clearly. Crucially NZ schedule was quite light for a such a long period. We did lose him to international duty on a couple of occasions, 2012 he was gone for about 6 or 7 weeks as NZ toured India and 2017 he was part of NZ's Champions Trophy squad. He also turned NZ down on a couple of occasions so as not to jeopardise his Warwickshire contracts. He was a bit more highly rated by his country than you may think. And rightly so.
We've struggled with T20 overseas players for so long. Shoaib Malik in 2014 was good for us but even he missed Finals Day for the CPL (I think?). Even Jeets, as incredible as he was, used to get caned in that format in his 2 or 3 seasons with us.
I think the only way you can guarantee player availability (fitness permitting obviously) is to engage a domestic player from SA, Aus or NZ who is largely unheralded and not really on the radar of national team selection. Even then Cricket Australia are so difficult to work with, look at Kent and the Xavier Bartlett situation, all agreed for all formats, then on the eve of the season CA pulled him out and only let him play the Blast. Nightmare.