One of the things that one needs to take into consideration, is that SaaS (Software as a Service) is not reliant on any technology, in other words you can write SaaS with any language or framework.
With Coldbox, this doesn’t mean that Coldbox can’t do what you are looking at achieving.
What you need to do is sit down and work out how you are going to deploy this, and make it available to your clients. That means security, what is displayed if anything, or just returning data that the client will display.
Many factors are involved.
Modules in Coldbox do make SaaS easier because you can add modules to your SaaS, and then define who has access and who doesn’t with greater ease. Whether it is Coldbox or not, you still need to take the security and access into consideration.
So lets say hypothetically speaking, you create a module, which is just to provide map locations. Then you would design this to the technology and framework in question that you choose to use. Coldbox makes this easier, because you can before the module is called, see if the client has the rights or no longer have rights to use that service. How you do that is not Coldbox specific, but can be made easier because of the framework.
So in that example if you selected client A as having access, and client B doesn’t, then you need to know how you are going to handle that. What is provided back as a means of, whether the access has expired or they just haven’t purchased it.
The fact that you make reference to whether Coldbox is a good fit is not the solution you are needing, the solution is how you intend to secure the SaaS.
Hopefully this makes more sense, or if you have a specific question in how to secure the service then maybe we can help more. But the answer is anything that you can think of developing, can be achieved in Coldbox, it just boils down to implementation and requirements you need to secure the SaaS.
As for what you can use modules for, have a look at ContentBox. This made up of several modules that provide the final solution, but lets say you want to redesign the Admin section, then you have a module that could be easily modified to do this, without effecting the rest of the site.
Another good use of modules is portability, designed right, you can just copy and paste it to another Coldbox application with minimal changes and it should just work. But of course there are hundreds of examples on how you can use modules.
For example I designed one site 4 years ago, every single line of code to the application, was considered shared code. I wrote 15 modules for this application, in which around 45 domain names pointed too. The only difference was the code to change the datasource for ORM based on the URL, and the same code and modules could be used to service any one of the 45 domain names. In my case I added extra functionality, to switch on and provide security via interceptors.
Which made sense for this client, because they had many aspects that where identical, so modules and the ability to switch on or off per client was made based on who was viewing which URL.
The upside to this, was no duplication of code, no extra mappings or virtual host settings, instead all pointed to the same code base, and due to configuration options, then one module could be available or not.
What you are trying to achieve sounds identical to what I did 4 years ago.