One thing to take into account - the AI already uses the 4 starbase per sector rule - not the minimum distance rule.
Now as far as I can remember, it only said that you would only be allowed to build 4 starbases in 1 sector.... not that there would be a total, all races included hard cap of 4 per sector. I might be wrong as it has been a while since I read it!
On your points
1) Theoretically, you could do that if the AI followed the same rules as the human did now. It would take a larger number for sure but it is equally possible. Further, I think, should the new rule come in (and it is a hard cap 4 total per sector), that the AI would be made to be aware of the potential monopoly and simply destroy your crappy starbases.
2) At present you can nearly match that anyway seeing as the radius of a starbase allows for 8 sectors between in a vertical/horizontal line (depending on just how short you mean the route is). You start with 1 on the first point of the trade route, let's say it's running directly horizontal, then put 2 each way vertically. Move down four squares along the route and repeat. You would only need a 9 parsec route to achieve 16 (actually 17!) starbases under present conditions.
Obviously, your way would mean that each starbase would give full coverage... but it would only be able to run for 16 or so parsecs under those conditions and you could add more on my little picture to simulate more cash.
Hmmm time to try and draw a funky dot picture to illustrate my point.
o = empty parsec
X = starbase - the middle line being ones directly on the route
p = planet
R = route
ooooooooXoooooooo
ooooooooooooooooo
ooooooooooooooooo
ooooooooPoooooooo
XoooXoooXoooXoooX
ooooooooToooooooo
ooooooooToooooooo
ooooooooToooooooo
XoooXoooXoooXoooX
ooooooooToooooooo
ooooooooToooooooo
ooooooooToooooooo
XoooXoooXoooXoooX
ooooooooPoooooooo
That's 16 without putting a further one 3 parsecs beyond the planet that the route terminates at. It's more a case, I think, that if someone could be bothered to do that then they would also be bothered to do it under the new system. I personally like longer routes to make more money!
And, there is the cost factor (and sheer hassle) of getting that number of starbases up and running anyway - as long as the route has coverage, I dont bother overlapping intentionally.
The main thing I think wrong with the current situation is AI starbase spam. It doesnt particularly bother me as I just declare war if they are in my way, or buy them off a (purportedly) friendly AI.