Why don't you install apps2sd. it makes the process much easier to move things. The important thing to remember about space not used is that it's space not used.
I don't see this as an issue as more and more apps allow SD operation. Archos could change this but to do so would require a full reformat of all memory unless it could be done with parted. You could do this with the developer edition. For most users there is some traumatic risk.
You could also write application developers that don't enable SD operation. The whole idea of enabling this in Android was to make device storage moot.
I guess you don't get it. Apps2SD means NOTHING. It will move SOME of the app to SD but the Dalvik-cache which is what the JIT builds for EVERY application on the system remains in the system storage. Seeing that we have only 256 meg it gets used up QUICK even with moving apps2SD w/ Froyo. That's why devices like the Incredible, Evo, Galaxy S, Droid X, etc... have a far greater partition size. 256 Meg is no different on the A70/A101 than the original Droid running Froyo. Archos needs to address this issue ASAP or these tablets will be relegated to the bargain bin awfully quick.
The default Android file system has the Dalvik-Cache in the /data partition. This partition resides in the system memory. This is also the partition that has only 256 megabytes available for application installs. Depending on the application, its' size and the amount of applications you have this can be used up quite quickly even after moving the app2sd.
EDIT: For instance my son has Ninja Jump, Madden 11, Angry Birds, Angry Birds Seasons, Jewels, Kindle and about 15 other assorted applications totaling about 20 meg. He has 134 meg free of the 256 meg initially available. These are all moved to SD but like I said the Dalvik Cache remains in system memory. This is where the system memory needs to be paritioned to a minimum of 2 Gig in order to prolong the usefulness and life of the device.