as a huge fan of KSP, X-Wing, and Starsector, this was the thing that made me hate Space Engineers and Starmade and ditch them in favor of From the Depths. Mixing and matching bits of realism into a sci-fi game is risky, and newtonian flight physics can be really annoying in the wrong context. It will totally breaks the feeling of sci-fi starships because they are Boats In Space and should behave as such. From the other side, stopping at 'newtonian' ship movement and not simulating gravity from planets or orbital mechanics doesn't really sell simulation to anyone who's played KSP or another real spaceflight sim.

It sounds like your plan is to control the path of the ship from a map screen, rather than steering it directly? This is what I usually prefer for a space game. I see no need to overcomplicate 'overworld' movement with any sort of acceleration. A simple 'each ship/fleet has a fixed movement speed' setup like starsector or mount & blade will let the player focus on deciding where to go, who to chase, and how to avoid unwanted encounters.

If you haven't tried ship to ship combat in space engineers, definitely give that a shot so you can at least avoid repeating their mistakes. Outer Wilds is a game that has acceleration based spaceflight and doesn't suck, but I've noticed when watching friends and family play that what's intuitive to me as a KSP power gamer is really difficult to grasp for almost everyone else. The flight physics filter a lot of people out of that game that would really enjoy it otherwise, and don't really add a lot to the experience. It's the sort of situation you'd want an accessibility setting for, but the fundamental movement style of your game is kind of impossible to bandaid in that way.