Build a ship. Pretend it is a bunch of sectors, with the core as your start and your destination off elsewhere. Try the line method. Make a line of 20 blocks in one direction, 20 in another, then 20 in the third. Add one block to every side of the \"path\" to represent the sectors that have loaded around you as you fly.
Next, do this again, except make it diagonal. That is to say, one forward, one side, one up, one forward, one side, one up, until it has gone 20 in each of the three directions. Now repeat the \"padding\" again to similate the sectors you have loaded around them as you fly through.
Compare the mass of the two ships you have made. Guess what? There is very little difference! You put MUCH more load on a server by having speed limits at 100 then you ever would having speed limits at 50 and being able to navigate in a straight line in a diagonal (which when drawn through cubic sectors results in the same ones being loaded as you would get if you turn every sector).
Besides, if you are in a small enough ship you may ALREADY fly (sector-wise) in the \"straight line\" because you turn fast enough that you can just follow the indicator.
The only problem that needs to be dealt with is making sure the game can display an indicator for someplace 50 kilometers away (which means that the indicator cannot be just highlighting the sector like it currently does, as said target sector may not be loaded yet, but has to be indicating a non-existent \"beacon\"). Whatever system is put in for this may actually be useful for other things too. For instance, perhaps it could also be used for a \"map mode\" in which object hud indicators are temporarily hidden, and instead beacon indicators like this are shown for every object you have deemed to be of interest. Not great, but it would beat the current cluttered excuse for a map-prototype.
And Schema has already indicated that he is getting rid of solar system sector rotation mechanics when he gets some time, and will be replacing them with planet-specific ones instead for the day/night cycles.