I don't have a first, let alone a second A500, so i'm not sure that's a good answer really. However, the ACA500 is equipped for CF's and atapi devices, so the A570 isn't really a huge dealbreaker, i think?
Also, if you guys are lucky, it's not going to be impossible to hack away at this, and remove the "blockage" to be able to use legacy add-ons. At which point Jens no longer has to provide support, you've modded his hardware way beyond spec, and everyone should be happy. Obviously i'm hoping for "artificial" blocking of the expansion port, meaning anyone could open it back up with a rotary cutting tool on a "multi-tool" type driver.
Time will tell. So far Jens have been VERY good to me, and provided not only a good speedboost to my A1200, but with it a size A memory upgrade, and add to injury, the Indivision MKII lets me play K-240 at home again. Still not on the Telly, but at least i'm playing again. My point is, don't take losses out in advance, you may yet be happily surprised.