Thank you for your feedback. What I really need to know in order to decide whether to disable path explorer data saving in relation to the server game is whether, on average and overall, joining is now faster or slower, otherwise reverting this may make things worse (on average and overall) rather than better.
As to the size of the server game: the eventual data size is difficult to predict for any starting map size without actually attempting to start at any given time. What matters, of course, is not the size of the map in tiles but the quantity of towns and player transport infrastructure. Once this map reaches a few years beyond the present day, I intend to make the next map somewhat smaller in size (~400-500 towns instead of 760 as in the current map), which should help matters. I notice that there are still, by 1951, large areas of the map not reached by transport networks, suggesting that the number of players interested in playing this game and able to join the server is less than the number of players needed to develop a map of this size fully, suggesting that a moderately smaller map would still give ample scope for enjoyment.
However, I do want a map physically large enough to make air transit and shipping interesting.