Seen from a distance any soiral galaxy would look flat, just as the surface of the earth would seem a perfect sphere, this however does bot equate to movement beung locked to a highwaygrid. It is the asymetry of manouver that makes warfare interesting, it us what allowed the finns to pummel the massively superior red army, how Hannibal took theromans by sufprise and the japanese to conquer manilla. The germabs to bypass the maginot line, twice.
So even in a seemingly flat, two dimensional plane, asymetric movement is key to warfare.
The way I see it, Hanibal, the finns and a number of other combatants were still working on "hyperlanes". Instead, they got ahead in the research race and got up to technologies that allowed them to use "hyperlanes" that weren't yet available to those other empires. Alternatelly, they decided to brave "hyperlanes" that went through highly dangerous zones of "space", building an army that was mostly resistant to those threats to reach to their targets in fighting condition.
Warp vs Hyperlanes would be more like one side moving mechanically through the land (by walking, riding a vehicle or so) against the other side "phasing out" of space-time until the earth rotated, and then reapearing the same "fixed" space - The way of moving of both sides doesn't interact. War is much more chaotic in that sense because you don't have a way to control or restrict the other side's movement, and you can't actually set up any kind of preventive measures (patrols, controls, etc) - you move in completely different ways.
That said, I still hold that warp is just a densely packed version of hyperlanes with short length, and that wormholes are also the same just with a slightly different set of parameters, so combining them all and making them appear as different would actually be rather simple. Most of the complexity comes from trying to represent all them through geometry in-game. This is why I don't really think that the FTL modes are that different at all. All of these changes could have been done by controlling system placement and generation and travel distance to limit the number of available travel rutes from one system to another (this is the real quid of the question - right now, due to how dense the graph is, there are a countless number of routes from any system to another, which is why it's so difficult to defend points of interest - which together with the way the current wargoals system works is why defensive tactics don't work).
The real discussion is IF you want "chokepoints" and "strongholds" to be part of your space opera landscape in the first place. Personally, I do want this, so a change that will make them viable sounds good in my book.
If I had done this, I would have gone in a slightly different way: instead of naturally occurring hyperlanes and accidents restricting the passage to certain systems, the owner of the system would be able to "seal" certain pathways to the system - so that you can create those choke points yourself. Think about it as if you were making the system undetectable from certain systems/directions. Higher level technologies might allow other players to bypass part of those restrictions, and naturally occuring accidents might impose limits to this (for example, pathways to a high energy star might not be sealable, and paths from neutron stars might not be sealable, so you have to build your network around those). If you've played Dungeon Keeper, it's more or less like fortifying your dungeon.
That way you still have the "open space" feeling, can still include things like terrain and accidents, can offer tactical advantages and the possibility to create chokepoints and strongholds, don't have to rely on having to build fortresses / attractor fields along your border, and don't have to worry about pulling a fleet outside of its normal pathway.
