I have tested all my systems developed in Delphi (in Windows XP) on Wine (OpenSuse Linux) and they work perfectly. My question is: should I start distributing my systems (on a local basis that I can support) as Wine ready or are there other issues I should take into account?
You could do what Google does and package Wine with the application. That way there's no fear that Wine will change something in the future and prevent your app from working.
Yes it would be a good idea. All that can help communication between the worlds of Linux and Windows is a plus. It would be even better if you can have your code compile natively in Linux.
Personally, I'd love to see apps available that are 'pre'-crossplatform like you've described.
@Mark's answer is also a good idea: distributing a statically-linked edition of Wine, while it would make your product bigger, would ensure that it will run, even if a newer edition exists that breaks something (I'm reminded of places that ship their 'own' JRE to ensure their tool runs correctly).
Maybe there should be a move made in the Wine community to have "made for Wine" stickers/logos available?
I would post a notice that your application has been certified to work with WINE version whatever, and that it may or may not work with other versions of WINE. You should consider testing your application with the beta and rc versions of wine to ensure they will remain compatible during release cycles.
It is simple enough to sandbox you WINE installations.
Getting your application to build with Free Pascal and Lazarus would be a huge gain on Linux systems, at the cost of some pain to you.
You should list Wine as a supported platform, say which version of Wine you've tested with, and ask to get added to the list of apps that support wine at http://wiki.winehq.org/AppsThatSupportWine
IF you application runs in Wine, can you not try compiling it natively and linking against the winelib?