Um, no I'm not looking to be richer, faster, buy doing less trade... I already have more than enough credits acquired through non-trade related activities to make credits a non-issue for the next couple of decades. What I would get out of a Panther is a reallocation of my time towards other in-game activates that I already enjoy, a little more variety in my otherwise very Cutter-heavy fleet, and the novelty of a new ship. The amount of hypothetical additional imbalance is pretty small beans by comparison.
the literal only function of the ship as it would exist as just a new ship with no other game changes is to provide a larger cargo hauling capacity to reduce how many trips are needed to transport commodities. and the way this would be 'balanced' by fdev would be making it expensive... which as we know is not a valid balance. you suggest this would be marginal in terms of imbalance but the hypothetical cargo capacity ranges from 1000 to 3000 depending on guesses thru time. that's a 30% to multiple times reduction in time to make the same amount of money trading. given how the ship is balanced to be expensive, this means only the rich will get to leverage this improved capacity and thus reduced time to gain money.
I'm not sure if you are conveniently ignoring how that works or just trying to pretend like it doesn't exist that way in the hope that it actually becomes an option you can exploit.
my view is that this ship would do more harm by further imbalancing trade unless it coincides with additional gameplay that creates a balance mechanic that doesn't allow the rich to simply get richer doing the exact same activity they were doing with lesser ships with absolutely no additional effort/skill/risk or activity. that without that additional gameplay, you guarantee that it involves less of all of those things.
Your last paragraph is too much slippery slope and strawman for me... There are plenty of people out there who actively enjoy space-trucking. I'm not one of them, but ED absolutely caters to that crowd as part of its overall offering. Adding some complexity (not the same thing as difficulty) to the space-trucking game-loop would be worthwhile.
If one were looking to inject some additional challenge/game-play within the context of Hauling, you could add an FSD experimental to allow using Tritium cargo to synthesize jumponium. +16/32/64 tons of Tritium for +300%/500%/700% jump range wouldn't change maximum jump ranges in the game (carrier still wins), and wouldn't do much to change small explorer ship builds as they can't really afford the cargo space. It would allow large haulers to more effectively compete with Fleet Carriers in hauling, and it would inject another cost to balance against the profitability of the hauling run. Add a requirement for the tritium boosted jump to originate from a Navigation Bouy instance and you would increase the time the hauler is subjected to interdictions without increasing the overall time it take to make the run (trading less time making hyperspace jumps for more time in supercruise). Pirates might appreciate that.
Also, anything that creates player-driven demand for commodities is a healthy step towards a more dynamic and interesting economy.
except you don't really create any demand for any given commodity. you just create demand for the most profitable thing at the time, which is generally limited to a handful of the same things. so the demand is the same as before the ship for the players playing the space trucker or 'i wanna be the richest ' game. this doesn't help any of that become more diverse or different at all. you get a temporary bump from a new toy but that is quickly over since you have basically infinite money to buy everything and then you are back at the status quo.
large ships need their own place in the game with their own unique gameplay. the game is too geared towards balance of small and mid sized ships because fdev apparently set things up thinking like a single player game and totally ignored how player's would circumvent their fog of war by collecting data and rendering their fake economy and assumptions of income rate impotent. then the boredom from lack of gameplay leading to rebalancing everything from income to jump distance etc has only exasperated the problem with large ships.
so much of the balance seems predicated on this obsolete assumption that wealth takes a long time to get and that the galaxy is dangerous so expensive ships are risky investments. that hasn't been true for years and in terms of risk, never. just adding a larger ship may not significantly change the status quo of the game for rich players, but that's mostly because the game is broken for them already. it does impact new players who will recognize this for what it is... which is a way for already established wealthy players to extend their gap and all the advantages that wealth gives for the game mechanics that involve other players... and basically an 'i win' option for trade.