I kinda don't think warm-up matches should be necessary at all in this case. All the players are either coming from series against Sri Lanka and India before that, or else the domestic season playing both 4 day cricket and t20s simultaneously.
I understand that the players want preparation but there's also a balance issue and cramming in series into a season. They'd do better to look on a case-by-case basis.
Especially the t20 stuff. a little silly IMO.