Andrew, some good thoughts there, some I'd thought of some I hadn't, and my final solution utilises a lot of your thoughts. Looked at many clubheads on offer, don't like any of the weight port ones. Have decided the easiest way forward is to make a 2 part set with the 3-6 iron matched and then the 7-SW matched.
So I've decided on the Golfsmith Tour Cavity Forged clubheads. These come with the extended hosel where, below the shaft insertion depth, you can insert up to a 10 gramme weight. The makers specifications also indicate that these are designed to allow for up to a 3 degree crank in both loft and lie angles. Plus being forged future tinkering is not going to be a no-no. Here is how I plan to work the set:-
3 iron = 4 iron head, cranked closed from 24 to 21 degrees, lie angle up from 59 to 62 and head weight increased from 247 to 261. Tricky bit is the extra 4 grammes over the 10 gramme hosel port weight, but reckon is achievable.
4 iron = 5 iron head cranked closed from 28 to 25 degrees, lie angle up from 60 to 62 weight up from 254 to 261.
5 iron = 6 iron head cranked closed from 32 to 29 degrees, lie angle up from 61 to 62 weight stays standard
6 iron = 6 iron head, loft cranked open from 32 to 33 degrees lie angle up from 61 to 62 weight stays the same
7 iron = 8 iron head, loft closed from 40 to 37 degrees, lie up from 63 to 64, weight up from 275 to 289, again an extra 4 grammes to add.
8 iron = 9 iron head, loft closed from 44 to 41 degrees, lie stays same and weight up from 282 to 289
9 iron = PW head, loft closed from 48 to 45 degrees, lie stays same, weight stays the same
PW = PW head, loft opened from 48 to 49 degrees, lie and weight stay same
AW = AW head, loft open from 52 to 53 degrees, lie and weight left as is, though head is 5 grammes more
SW = SW head, loft open from 56 to 57 degrees, lie and weight left as is, weight is 11 grammes more than wedge.
These will be fitted with S300 shafts, 4 trimmed to my 6 iron specs and 6 trimmed to my PW specs. I'm going to spend a bit of time making sure that I'm really happy with the intended shaft lengths before finalising. But at present I'm looking at a floor to butt, parallel measurement, for the 6 iron as being 38 inches and for the wedge as being 36.5 inches.
I'm waiting to hear back from Golfsmith on a recommended retailer/clubmaker in my area.