Choosing 4E Spaceship Propulsion

[Seneschal]

I'm looking for some experienced advice and criticism, since I can't seem to decide on a crucial worldbuilding detail. My group and I have played a few sessions in a nondescript space opera setting some time ago, and we've enjoyed it enough to want to continue. I've decided to thoroughly flesh-out the setting before we start again, going with the Sci-Fi kitchen-sink approach, and then taking out elements that don't fit the tone. Now, we've agreed to keep it (relatively) light-hearted and adventurous, with very high TLs (around TL 11 mostly), rayguns, space pirates, interstellar kingdoms, psionic powers, that sort of thing, but we also wanted to establish some ground rules and keep it consistent. Less space-fantasy and more far-future-tech advanced enough to be miraculous.

However, the question of space travel (both interplanetary and interstellar) is giving me headaches. I can't seem to find a compromise between gritty enough to be interesting, and handwaved enough to be unobtrusive. I only managed to narrow it down to a few prerequisites and key issues:

1) My players expressed the wish for non-instant stardrive, something like Star Trek warp or Star Wars hyperdrive, but we haven't decided on the speed yet. I personally think silly quantum probability jumps would be a lot of fun. They'd be allowed to visit about 300-500 parsecs, and I'd like to avoid communication- or travel-times over 6 months.

2) I'm not quite sure how "connected" I want my star systems to be. Should inter-system jumps/hyperdrive be unavailable? If we're going for a theme of frontiersmanship and a dispersed, decentralized humanity, what would be more suitable?

3) I'd like it if there was some fuel consumption or resource management to anchor the PCs more closely to planets and space stations. However, we've already introduced advanced technologies, including artificial gravity, which should eventually lead to a bias or diametric drive, if not something even more advanced. Would that suit a space opera better, and am I just giving my players unnecessary busywork?

4) I've considered speed-of-plot interplanetary travel, but I can't really justify an abstraction like "1 AU per day" in 4E Spaceships rules, or use it in Spaceships combat. 3-4 days for an Earth-Mars voyage (or its equivalent) sound about right for pacing purposes, but it requires such ludicrous velocities that it begs the question why I'm even bothering with realism.

5) I wouldn't want to have just one type of engine, purely for diversity's sake. I'd prefer there to be a difference between sluggish (1G or below) long-range ships and snappy orbital ships or combat drones that can't maintain thrust for more than ~30 minutes or so.

6) A minimum of plausibility would be welcome, even barely-coherent technobabble. I had to suppress most of my hard-sci-fi instincts for this setting, and think more in terms of drama and emotional weight, but I believe some consistency can't really hurt as long as it doesn't interfere with gameplay. I've been scouring tvtropes for fictional examples to copy, but I've got nothing so far. Maybe you guys know of some speculative propulsion system that I could use.

I may wrong on all of the above - if you think something else would represent the tone of the setting better, feel free to correct me. So, what do you base your tech choices on? Has anyone run into a similar problem? What would, in your opinion, best suit a space opera? I'd appreciate any advice you can give, much obliged.