Yes, you could use a UMTS USB stick (or the future 5G) and an external microfone along with the Archos 5 to make phone calls (IF it had the necessary phone software), but that would be the most awkward phone I've ever seen.
You can simply keep your FM remote control and headphones so you can easilly pick it up to place Skype calls or to receive them when the Archos wakes itself up on incoming calls (considering the software might support something like that).
It's basically the same deal as those people that always use headsets to place calls.
But anyways, the Archos strategy is to tell people to use any $8 phone to place phone calls, the rest can be handled by the Archos 5G or the one with the dongle.
Archos tried to copy some elements of the iPhone user interface (flipping photos, scrolling without touching scroll bars, fast scrolling by dragging and then releasing, etc.)
Actually, Archos has had these features since 2004 with the PMA400 device.
I really don't see them competing, even if they have features in common. They're on different markets.
Actually, they are on the same market. The same type of carriers are going to be selling the Archos 5G at about the same price or cheaper then the iPhone 3G.
For example if O2 has the iPhone 3G, then it's going to be Vodaphone, Three or T-Mobile that is going to have the Archos 5G, if it's Orange that has the iPhone 3G, then it has to be SFR to have the Archos 5G, if it's AT&T that has the iPhone 3G, then Archos is going to have to partner with one of Sprint, T-Mobile or Verizon. You can't be more competing then that.
Archos and its carrier partners are going to be saying stuff like "Don't buy the iPhone 3G, we think you will have a better choice in choosing the Archos 5G and this $8 mobile phone for calls". Basically that is what the salespeople are going to be saying in the stores.