You want what I have!
I've spent a long while engineering and tweaking my 'Conda into a long-range multi-role format. My current build gets over 51LY range, while still carrying enough weapons/shields to do a HAZ RES, an SRV for planetary stuff, and I can swap out cargo racks as needed for whatever missions I'm into at the moment. I can also swap in Passenger cabins, but those are heavy and reduce the jump range, so I leave them off unless I really want to do passengers for some reason.
You have to balance a lot of things, and each person is likely to have a bit different preferences. I want good jump range, tough shields, sufficient weapons to fight back, an SRV, cargo space, utilities.
For example, I could get a better pitch/yaw rate with class A thrusters, but wow are they heavy. So I fussed around for a bit, and managed to engineer some 7Ds that are still quite a bit better than stock class A's. That's good enough for me, the way I fly the ship (I'm not a dogfighter -- I fly it like a battle wagon).
Another example, I'm using pretty small shields, but I've engineered them a lot, plus added light weight but heavily engineered boosters as well. The MJ count looks small, but these shields hold up in battle against NPCs quite well. And I have a shield cell bank just in case.
Other people might want other things -- more weapons or whatever. But those are the decisions you make when tweaking a ship. My weapons can fire almost forever on 2 pips.
I've been running this build for a bit now, and it's very nearly perfect (for me, anyway). The ship can handle any PVE task. CZ's might be a little dicey if you're not paying attention.
Anyway, here's my build, perhaps it'll give you some ideas. (My actual build in-game is slightly different because I didn't get the exact rolls I wanted, but it's close to this -- I get about 1 LY less).
https://eddp.co/u/A8dss3qU
Have fun out there!