In the discussion of scanners with ken and nyranth, working a setting without stealth is not such a bad thing. I think the sooner we move stealth away from being "invisble" the sooner we can build a new technical doctrine in space warfare that accomodates the science.
Stealth does not have to be undetectable, it can be deception. This deception depends on how much trade volume happens in your scifi setting and how much heat generating junk fills a system. Just looking at the potential GDP and waste we make in our backyard on earth, i wouldnt be surprised that we have a potential to litter a system with old fission rods and unrecovered drones.
So combat is about overwhelming the other sides sensors. It makes sense that on the most basic level a civilian ship scanner has a resolution of ~4 frames per minute. This gets better as we get better bridges. With a Standard or Large Cockpit we can ~40 frames, and at the Command Bridge Level ~6 Frames per Second. The data and the resolution gets better with more computers and sensors act in gestalt.
In "silent running" crewmen can put on their vacc suits and turn off life support, reducing their heat signature. I don't know yet how much to change things in the rules as i mentally walk through considerations. I don't know how much shielding can hide heat yet. Although I'm am more certain that these factors can be figured out.
Defending should be easier with decoys, drones and pods roaming a system. Fortification is creating a mess of heat signals and follows the same mindset as underground shelters, confuse the enemy. Prevent them from determining the true nature and extent of the defenders.
Pod or Drone launchers are a kind of ship that will be very useful in such a setting. They are useful in efforts in deception and misdirection serving q-ship or system defense vessels that come with a special surprise. They specialize in adding confusing signals in combat encounter.
With so many decoys, stealth hulls are about appearing as something else and presenting a misleading profile to the enemy.
Asteroid fields, rings and clouds of debris are the best defensible position in a system. There may be efforts to set about artificial rings as a source for cover for planetary space fortresses, and a resupply source.
Moving forward I guess I have to peg my assumptions and re-imagine my naval combat. I'm currently sticking to RAW for maximum user support, but I guess down the line If I can, I'll have to develop a better ship building method. Out of curiosity I'll ask my friends who can sketch out in "back-of-the-envelope" calculations what it would cost to make a Blender Game Program that just builds Ships, Star Systems and Planets for Sci-fi writers and GMs. One of those things I'd like to do if money was no problem and there is sufficient demand.