"the old one for instance included Pataliputra within the borders of the Indo-Greek kingdom - this dosent make historical sence, as a dynasty which lost its capital would not later be able to negotiate a peace treaty along much larger borders" why should a dynasty have to topple, you write it as though it is inevitable that the Sunga line should disappear if the capital were lost.

"we do not even know if the Indo-Greek kingdom ever ruled that far" than you have not read PHG's side of the debate, as the Yuga Purana mentions how the Greeks caused society to collapse by imposing their own social ways and how it seemed inevitable that Pataliputra would fall. Then there is Strabo who mentions them of temporarily holding lands upto the Ganges.

"how the example of some other maps choosing that route means this article must" I fail to see how this part of history is being treated differently from any other. Also you seem to brush aside the mentioned articles about the Roman Empire and Achaemenid Empire as though they are insignificant or of little value to learn from (editing wise). Considering those artciles are of high importance and would attract a lot of interest, it has been edited in such a way that has deemed fit and that wikipedia seems to follow such a policy where a political entity is shown by the greatest extent that it has encompassed geographically. So to stay in league with other high quality articles it would be in the articles best interest to follow suit.

"lost its capital would not later be able to negotiate a peace treaty along much larger borders, as indicated by the Heliodorus pillar" the Heliodorus pillar was erected 60 years after Pataliputra was taken by the Greeks and within the same was taken back by the Sunga Empire.