Hey there!
The offset isn't determined by the diameter - it a functional requirement of the width of the rim/tyre (which of course will likely change with the diameter anyway) and is generally only a consideration for either tyre clearance to struts and steering components and the arches. Although it can be calculated - it doesn't necessarily mean that something wont get in the way!
The other consideration is the slightly changed arc of the suspension which is really something else again.
On tyre/wheel width the first two in your example are identical at 6.5J so any change would have been be for the geometry question - in this case 3mm..
To go up an inch in width would need careful consideration of which way to offset the wheel to maintain inner clearance you would change the offset to push the wheel out, and vice versa - or split the difference.
Typically to maintain the inner clearance you would halve the difference so 1 inch wider would give you 12.5mm each side - so from a starting number of 45mm offset you would use an offset of 32.5 on the wider / bigger wheel but what to allow for the geometry? guesswork unless you get the dead hard sums calculator out and work back to what the manufacturer has in mind
On a car you could also increase the rim width but less so on tyre to an extent to 'round out' the profiles - tyres for this wheel could be anything from 205 through to 235
Picture here (if I manage to attach) is of 355 on my old Pontiac! I did a lot of playing around with tyre's and wheels on that one - they didn't seem to last long
