Question on approaching development

Hi there, I’m a 6 yr CodeIgniter veteran developer with a large number of CI projects, mainly based around Firebird SQL, that I develop & host for clients. Despite such a long history with CI, I’m relatively new to EE but came to it because I have many clients that don’t need a full-on web application developed for them - they just need a quality website with the ability to control its content. EE is a perfect fit for them.

However what I’m finding is that many clients want a ‘hybrid’ of what I do. They need a portion of their web site that is fully dynamic, interactive and performs business transactional functionality (the kind of stuff that I typically build from scratch in CI). But they want all the standard functionality of a general website (ie. About Us, Contact Us, Home, products, services, etc.). So what I would like to do is combine the two, but I want to do this in such a way that it is future upgradeable yet doesn’t restrict what I need to do outside of EE.

Since most of my transactional systems have a Firebird SQL database on them, they want to extract data from those systems and present them in their EE site. I could do a webservices SOAP integration, but I’d then have to code EE to present the data and handle interactivity using the XML data from SOAP as its data source. Since the databases all reside on the same server cluster, and I can securely link EE and CI apps together, I can just provide that functionality inside of EE somehow.

The question I have is what is the best way to approach this? Should I consider plug-ins for this? I’m not sure if modules is what I need because I don’t really need any back-end admin management to these systems in the EE control panel, but maybe I do? Not really sure.

Or should I just create a subdomain off their website and put this content on an entirely separate CI application and just use iFrames to show it within their EE site?

Open to all ideas, suggestions, best practices, etc. I’m not one who likes to reinvent the wheel if I can help it, but I have legacy systems I need to integrate with so that kinda limits my options a bit.

Thanks in advance for any input.

Myles