You're looking at this from strictly a balance perspective not a business one. Your two suggestions would certainly address the symptoms, yes. Yet it would destroy the demand for the Panther Clipper from a fiscal perspective.
The Panther Clipper will live or die on it's ability to outclass existing cargo ships significantly. That is where we, the consumer, are drawing the line. After all they could have announced this ship at ANY POINT over the last 11 years. Ask yourself why they waited until now?
I think you're massively underestimating the segment of the player base which feels that if it's not got the highest quantitative number - regardless of the actual impact on effectiveness - their build is a failure and not worth flying, and so will go to any lengths to get the biggest possible number. The Mandalay had about a 1 LY jump range advantage over the Anaconda and a few mild internal upgrades over the Asp, and was a massive hit (sure, there were people expecting it go over 100 LY, but it didn't and Inara puts it as the clear leader of the first four ships. People will spend hours collecting Titan Drive components for their FSDs when for in-bubble work a normal SCO FSD probably has the same number of jumps from A to B 95% of the time. People will G5 Lightweight a D-rated life support even though the actual impact on speed or jump range is basically nil. The Panther Clipper could be 850t cargo capacity and still get purchases.
You're also massively overestimating the financial impact of early ship purchases. Assuming that
every System Architect buys the Panther for ARX, and buys the ARX needed to do that - which is highly unlikely whatever its specifications are! - that brings Frontier about £300,000 over the exclusivity period. From Frontier's latest financial update, Elite Dangerous brings in about £6.5 million a year. So the most extreme case - 30,000 purchases if it has 2000t but no-one at all buys it at a "mere" 1000t - makes a 4% difference to ED's annual revenue. Obviously not everyone is going to buy it for ARX regardless of its capabilities, and plenty of people would buy it at a smaller tonnage.
Inara's stats roughly suggest that only about a quarter of the people who'd find a ship useful buy it for ARX during the exclusivity period - ownership there doubles nearly overnight when that ends, and then continues to rise quite a bit after that. So we're probably talking well under 1% of annual revenue marginal difference based on what precise tonnage the Panther Clipper has. Completely irrelevant.
If I understand correctly, the original Panther Clipper was so gigantic that it was extremely slow to maneuver.
It wasn't great, certainly, but it wasn't noticeably worse than other large freighters. FE2's combination of time acceleration, autopilot and no loss of power on turret weapons meant that you could almost fly it without ever
needing to turn it in real time, too.