I don't think this is technically correct. We haven't had many pace bowlers capable of hitting 150 kph playing for New Zealand, but we have had more than a few domestic bowlers capable of bowling this quick (and indeed even have some playing domestic cricket right now!). We certainly don't produce as many of these types of bowlers as many other countries (due to our limited cricketing population), but we do produce them. If I go back a few years (not too many) Heath Davis was pretty rapid. Speed guns weren't regularly in use back then, but I would be surprised if he wasn't capable of bowling 150+ kph. Unfortunately he was horribly inaccurate, and had real issues with no-balls. When Ian Butler hit the scene he regularly bowled in the mid 140's in limited overs cricket, and was capable of bowling 150kph. A series of very serious injuries meant he had to completely change his action his action, and never been near as quick. Richard Sherlock was very rapid (capable of 150kph+) when he debuted for CD (10 years ago), but injuries have ruined his career. Mitch McLenaghan would have bowled close to 150kph before he was forced to remodel his action after injury. Te Ahu Davis was very quick (if erratic). Milnes CD team-mate Andrew Mathieson is very fast, and considered to be just as quick as Milne.
My point is simply that pace alone doesn't guarantee you success in NZ cricket. Indeed the vast majority of our genuinely fast bowlers have had serious injuries - Shane Bond himself only managed 18 tests! What worries me is that many NZ cricket fans seem excited by Milne solely because of his pace. What was impressive about Milne's two T20 performances was his accuracy (at pace), and (as Larksea mentioned) his impressive seam positioning and variation.
I'm not suggesting he should go back to Plunket Shield cricket immediately. He has done enough to be included in the ODI side to play India, and I'm sure he will learn a lot there. However once these ODI's are over he should go back and play for CD, as there is no way he is ready for Test cricket. Test cricket and limited overs cricket are very different, and require bowlers with very different skill-sets. Milne may be able to bowl the odd 150kph delivery at limited overs cricket, but maintaining this sort of pace over a entire day is another story altogether! Milne's style of bowling is far better suited to limited overs cricket at this stage, as he really only bowls two main deliveries - the yorker and the bouncer. If you watch him play first class cricket you will see he really lacks the stock delivery he needs to be successful at test level. He needs to be able to build pressure on good batsmen - he still struggles to get our (3rd rate) domestic batsmen out, so I can't see how he is going to get the likes of Pujara, Kohli etc. This is not to say he won't develop into a good first class bowler, but the only way he can learn how to do this is to play first class cricket, and a test series versus India is not the best place to be learning!
In terms of the T20 side: In T20 cricket you need either wicket taking bowlers or bowlers that can get through their overs very economically (preferably both). Anderson fits neither of these categories. He is a very solid part time bowler, but their is no way he should be required to bowl his full compliment of overs every match. He can bowl good line and length, but he has limited variation and lacks a good yorker - top sides could completely take him apart. Ryder could fill in the odd over, but using part time bowlers such as Ryder is hardly ideal. God help us if we ever have to bowl Colin Munro. Having a few allrounders is handy, but Neesham at 8 and McCullum at 9 are largely obsolete in T20 cricket. If you are going to win a T20 match the vast majority of your runs should come from your top 5 or 6 batsmen. If Neesham is in the side he needs to be batting in the top 6/7 - if he is batting at 8 he is basically in the side as a bowler (as your number 8 shouldn't be doing a lot of batting in T20 cricket), and there are better bowling options than him.
Most successful T20 sides have at least 6 genuine bowling options. At the moment we have 5, and Anderson isn't really a great bowler. Having more options allows the captain to rotate the bowlers more, use different bowlers depending on pitch conditions, and stop bowling bowlers if they are having a poor day. If we were to include another specialist bowler (at the expense of a specialist batsman) this would give us 6 genuine bowling options, and with Neesham at 7 and N McCullum at 8 we are still going to have a very deep batting lineup. Ideally the extra bowler would be a spinner (especially for Bangladesh conditions). If Vettori was fit he would be the ideal option, but at this stage it looks unlikely. Ronnie Hira is probably next in line - he is an excellent fielder too, but I don't think he has been in great form. The form T20 spinner is probably Jono Boult, but he is unlikely to come into contention. Because of our need for another spin bowler both Kane Williamson and Anton Devcich will come into contention. Williamson isn't that suited to T20 cricket, but he batted very well for ND today, is a very good player of spin, and his spin bowling can be very economical at times. Between Milne, McClenaghan, Southee, Neesham, Mills, and possibly Boult we have plenty of pace bowling options.
