I would worry more about getting the most Wh that I could afford, than about the case becoming obsoleted. As tomjasz points out, the Reention Dorado case type is merely the enclosure & latch mechanism. Regardless of brand, they all have just two lengths & one latch type. No worry of the pack type becoming unsupported any time soon: There are a lot of companies building packs in those cases; Jenny Mao at Shanghai Aijiu Energy Tech, maintains a very good level of communication on this very forum.
Among ebikes which use Dorado style cases, all share the same latch type & one of two lengths; however, charge & discharge connectors vary somewhat from one bike brand to another: the Frey AM1000 v5 we ordered, uses a 3pin "mini XLR" type charge connector, & a 6-pin discharge connector.
MJ1 cells are certainly robust, but I believe Frey's switch to 35E cells was necessitated by LG's ongoing supply-side delays (as was a switch from Shimano to SRAM derailleur).
Notably, their 13s6p packs did not skyrocket in price concurrent with what I saw on other sites last year.
Comparing Frey's battery prices to a company like Biktrix is sobering:
$485 for the Frey 48V×21Ah with Samsung 35E cells (currently on-sale at $436.50),
$750 for the same size pack of 35E cells from Biktrix.
The use of Samsung 35E cells is listed on Frey's product pages; what isn't listed in the specs, are the BMS limits & thermal sensor I mentioned; nor the nickel plated strips. Of course every battery seller should specify exactly how their packs are built - it sucks that such details are not the norm across the whole industry. I don't know of any major manufacturer which gives such details; only lower volume builders who live & die by the premium quality of their work.
In particular, Bosch batteries really are nothing special. Not only are all their packs a mere 36 Volts, their largest capacity is 750Wh. Even worse, Bosch tries to lock their electronic components with proprietary coded connections. Aftermarket batteries for Bosch ebikes are available, but only because reverse engineering is legal so long as you don't duplicate the design. Here's what Bosch has to say about having a pro tear down your pack & rebuild it, when that #1 cell inevitably gives out before all the others: "For safety reasons, faulty, old or 'worn out' batteries should not be repaired or refreshed, but should be recycled appropriately. What's more, for your safety Bosch also strongly advises against having batteries repaired. If a battery is faulty, you must completely replace it instead." On the upside, Bosch puts a proper per-cell BMS in their packs... but so do premium battery builders who won't jerk you around with obstruction-in-the-name-of-safety, or "industry leading" prices.
I agree that Zen (& for other case types, also em3ev), would provide pack assembly methods superior to the packs from Frey; just request the right case type + connectors when ordering!
I too, have found that Frey is usually slow to respond to emails. I can only imagine how many they must get... & I only know of two people on their small office staff who are responsible for responding to all such inquiries.
That said, they have been willing to build with alternative components as requested (sometimes at no additional markup; for instance, forks to suit various trim levels are available pre-installed, at no higher price than buying one separately via retail; we did not opt for winter tires, but the price they quoted was less than I would have paid locally for a bare tire unmounted).
The Frey packs are a good enough value that I bought two packs, with the intention of parting out the first one that shows a bit of wear, to have a local pack builder reassemble it with a per-cell BMS. However, at this rate I may opt to have a 52V pack of 14s6p built instead: I am 6'10"\250lbs, so higher voltage helps move me more efficiently even on smaller motors. The m620 certainly gets better range per Watt from a 52V battery than 48V.
In fact, I'd say lower efficiency at low Wattages, is the main downside of m620 motors. At higher power, they run more efficiently & without even getting warm on a long hill. When comparing to a Bosch Cargo line or even a BBSHD, it just doesn't seem a fair comparison: Once the torque sensor is calibrated, the m620 feels preferable to any other ebike motor I've tried, at any speed.
('BaseVoltage' should NOT be left at 0 mV! A value between 730 to 760 mV is what the torque sensor will calibrate to, at 0Kg of pedal force. UART configurable m620 motor+controllers are still available: UART or GTFO.)
I'm interested to hear what you end up getting, & how it goes. Please let us know!
