Hi Robin,
I tend to recommend against using EA Lite at all, since it's very limited in its abilities. I'm pretty sure it can't access version-controlled models, nor can it do baselines. I also believe it won't run Add-Ins, which might be a factor in your case.
Another option for your deployment scenario is to use EA's cloud facilities. This does not mean you store your models on a Sparx server, but that you upload them to, and retrieve them from, a server of your own. Again, I don't know whether EA Lite can do this but I think not.
One reason not to use EA's integrated version control is that EA's set of permissions does not differentiate checking in from checking out. In other words, if you have permission to check packages out of the version control system, you also have permission to check them back in -- not what you want if you have any concerns about data integrity and the EA skills of your customers.
With the cloud storage model, you can specify read and write access separately.
Version control, which I wouldn't recommend for your scenario, requires the Desktop edition (the cheapest). Baselines and cloud connections require the Corporate edition (two steps up).
If you want to squeeze every cent, you can set it up so that only one user requires the Corporate license by making it their job to retrieve the models into a shared repository, to which the other users connect with their cheaper licenses. But you should also take into consideration the costs involved with managing different types of license and/or different types of client (if you do use EA Lite).
I'd say a DBMS repository for the development team, and for the customer either a replicated repository as Geert suggested or a cloud server. I wouldn't bother with version control at all, but use baselines instead.
/Uffe