To olsen:
Sounds good
But I have some questions:
1) What are the advantages of Roadshow compared to MiamiDX (lack of Gui is not a concern)?
You can rely upon me to be a poor salesman. Here are the
disadvantages:
- TCP/IP stack code is older than what Miami uses (Miami = NetBSD; Roadshow = 4.4BSD-Lite2)
- No built-in GUI
- Configuration works through text files
- No IPv6 support
- No built-in SSL support
- No ARexx interface
Here are some of the advantages of Roadshow:
- Significantly higher performance than Miami; according to my tests Roadshow is the fastest Amiga TCP/IP stack
- Uses far less memory once it's running than Miami, which means that you can run Roadshow on an extreme low-end configuration (Amiga 600HD with 2 MBytes of memory) and still have enough free memory available to run client software
- Controlled entirely through shell commands, which makes the whole thing scriptable
- Implemented a a single shared library, not as a big monolithic application
- Requires no assignments or shell paths to be set up, installs to your boot partition and acts as if it were part of the operating system
- Has a built-in DNS cache
- DNS client supports international domain names (ISO Latin 1 only, though), and transparently translates between the Punycode encoding and the human-readable form
- Built-in support for ZeroConf interface address assignment
- Comes with SANA-II drivers for PPP (modem/ISDN dialup) and PPPoE (ADSL)
- Supports the standard AmiTCP V4 API, plus a boatload of extensions which, among other things, allow for monitoring and manipulating traffic
- Source code for all configuration commands included in the SDK
- Developed and maintained by somebody who still answers questions and is likely to provide for support and bug fixes in the future

2) What kind of price do you have in mind (downloadable distribution)?
It's possible that this will be a downloadable archive which will have to be unpacked and copied to an installation medium. I don't know yet how it will come out, though, as I haven't signed with a publisher yet, and it's unlikely that I will publish the thing myself.
As for the price, I've asked around and the general consensus seems to be that you can't really charge more than 25€ per copy for this kind of software. Maybe add another 5€ for media costs and shipping. Maybe add some more if the package were to ship with a GUI.
So, I expect the end product price to be somewhere around 30€.
3) Will it be possible to pay by bank transfer?
If I sign with a publisher, this would be one option. I expect PayPal to be another option.
If those questions can be answered in a positive way, then you've got a customer right here 
Well, some of the questions are still unanswered from my own perspective. I know where this project is going, but the definitive answers will still have to wait a bit...