Yes, I tried it. The maemo version of mkswap accepts only the -L parameter and it gives an error about unknown parameter.
I also tried this -U from desktop (with mkswap and other tools too) but the "" always return an error message that UUID given is not correct (based on the UUID standards).
The only command that I found that clears UUID is tune2fs (works for ext3/ext4). Unfortunately the "-U clear" that works for other kind of partitions is not accepted by tune2fs for swap partitions.

If I understand correctly the UUID given by the system is created randomly (respecting the UUID specifications of course). You can very easily set any UUID you want with tune2fs. Since the chances of having the same UUID in a system are astronomical we can even use a preagreed UUID.
If I understand correctly you want flopswap to locate the swap on the internal memory automatically. I am in no way an expert to give you advices but can't the swap be located by:
I guess flopswap needs to load way before you can use something like this.

Thanks again for your efforts!