well the short version is ramming with drive bubbles is likely outright suicidal whereas a battle isnt necessarily.
so heres my idea: normal speed in a system is so efficient that even though it uses AM fuel the amount is so low that it doesnt even procc a single "unit"
my next idea: burn level isnt specifically the same between in-system and FTL travel
that is to say, it is a sort of placeholder that is a given based on the general knowledge of all ships in existence
i mean......we all have a codex, right?
so burn level is merely a representation of relative speeds compared between all known ships
also, s/u and burn level are completely independent from one another
i mean think about it, when you retreat you "burn" away at great speed
another way to think about it is once you break the sound barrier, you end up with a sort of bubble around you, whether mach 1 or 10
so once you reach a certain speed it takes all power from every system other than the main travel engines, thereby creating a massive flux field or "drive bubble"
this "law of motion" is perfectly stable and substainable at SUBlightespeed, but in order to "break into and mainly MOVE THROUGH hyperspace" you have to actually spend the energy from the AM fuel. again, having the drive bubble at all is perfectly stable and well within any ship (probably for safety reasons?) to maintain a drive bubble IF NOT MOVING even while in hyperspace.
the only problem i see with this idea is that conceivably youd have to come up with some reason why a fleet cant just use the drive bubble to keep other fleets away
besides that, youd have to be able to explain why fleets can battle in hyperspace without the drive bubbles battering them to pieces
perhaps it could work like this: the drive bubbles keeping them in hyperspace merge into one somehow allowing the battle to occur
or perhaps they just phase into normal space again out in the massive void itself, and phase right back to hyperspace
i think thats the best idea.....i mean the jump points are really there to help you navigate back to a system properly, as far as i can tell, and technically you could drop out of hyperspace at anytime, the only problem is youd be (technically) so far away from everything that itd be pointless
ok, so, the jump points are really just mathematical constants unique to systems that always exist which ships navigation are programmed to find
now, the only thing really left to explain is why you couldnt have the drive bubble just push fleets away
so, perhaps the way to explain this, is that once another fleets drive bubble comes into contact with yours, they sort of cancel each other out, and i mean actu8al close proximity, but since it is another fleets drive bubble and NOT a sold object (because the fields would meet before the ships actually met the other fleets field) they naturally cancel each other out, and if one fleet manages to get close enough they can pulse their drive bubble (like a really powerful indertiction pulse at super close range, tuned not just to stop the fast burn abilities, but to actually disrupt the field entirely) effectively forces the battle to occur, wherein you can engage, or attempt to disengage, and once a certain distance/time limit is reached then you can initiate burn and recreate the drive bubble.
anyway, im just spitballing