there are a lot of skilled individual genius trying to create the definitive "All in One" card

From my point of view: I did not set out to create an all-in-one card, I set out to create a network card made using "hobby friendly" electronics appropriate to the 30 year old Enterprise, so no little tiny surface mount chips, no magic programmable devices, just big old-fasioned chips. But when word got out about EPNET the constant feedback I heard was "more RAM", and then I heard Compact FLASH had an 8-bit mode... So it wasn't a case of "shall I do Compact FLASH or SD": CF was almost free and easy, SD wasn't. So it became a multi-function card.

And there has been more group work than you have seen on the public forum: lots of expertise (and even source code) from zozo on EXOS/EXDOS/Enterprise and lots of expertise on the internet/TCP/IP from lgb, for which I am thankful . Group work would be a lot easier if we lived in the same country!

Soon I will need help with something else: the User manual is ~50 pages, all in English...

card made using "hobby friendly" electronics appropriate to the 30 year old Enterprise, so no little tiny surface mount chips, no magic programmable devices, just big old-fasioned chips.

Mega like!

Ram/Rom and Mass Storage are the higher priorities for an user, I think, so  a cheaper upgradeable card can be also a big success.

SD is the ideal, but there are CF to SD adapters that can suit us.

Also exist a direct SD to IDE adapters.

Directly an IDE disk is nowadays difficult to find

I have least 100

and less useful than a CF.

Yes, mostly because it is need a external power supply. For a memory cards possible use 5V from the interface card.

On the other side, the SD is constantly evolving, there are a lot of formats, SDSC, SDHC and SDXC only compatible backwards.

These are only software differences, the Enterprise SD interface compatible with all, also including MMC.