“I’m curious; why would you want a player that runs on AA or even AAA batteries instead of the Li-Ion or Li-Poly batteries they use now? What advantage would there be? The existing batteries last 15 - 35 hours as it is; I doubt whether an alkaline battery is going to surpass that.”
The advantage is not having to worry about battery power remaining, or to connect the player to charge. One could carry some spare batteries and never run out of power. AA or AAA battery does not equal alkaline. There are high capacity nimh AA and AAA batteries. Most chargers charge up to 4 of these at a time. A player using a AA or AAA battery could be packaged with a charger and 2 or 4 rechargeable nimh batteries if manufacturers want to discourage use of alkalines.
"The typical re-chargable Ni-Cads "
Nicad is very old low capacity technology. Nimh AA or AAA batteries are far superior technology and hold much more power. There are now 2900 mah AA nimh batteries, and 1000 mah AAA ones.
“The existing batterries are ecologically-friendly.”
Are they? Is throwing away a player with a worn out built in battery eco friendly?
“I’m also interested in hearing your reasons behind wanting a full-size card slot instead of the Micro card slot they have now”
Full sized SD cards come in capacities up to 32 gigs. They also fit in a PC SD card slot without an adapter.
“AM radio? I’m with you on that one, in theory. I very seldom, if ever listen to the FM radio on my Sansa. My musical library is a helluva lot better, and there’s no commercials. But I would listen to various ‘talk’ radio discussions, news, etc. on AM ir it were available. the problem is the AM antennae and size. The player would have to be much larger and heavier than it is now, and with the marketplace and the competition going smaller & lighter, I doubt that SanDisk is going to reverse course 180 degrees and buck the tide! I sure wouldn’t if I were at the helm!”
I didn’t say for all models, just for one model. Some would prefer having AM radio even if the player is a bit larger. It doesn’t have to be huge though, just a bit larger.