These systems usually work well as far as standardizing and channeling changes to the site, however, they can be a bit impersonal and also have inefficient coding as Sam has pointed out. The corporate approach works well when it addresses the customer well, but most customers like to see the individual touch and am sure you would do a better job at that. Usually, the corporate decision makers do not want branches to do their own thing, but maybe you can convince them if you try to stick to main theme.
Another thought, if somebody is updating all the group's websites photos via a template system, then if you built the site and maintained it, the person taking the photos used vehicles could email you the photos, prices, models, etc. instead of emailing the central point, and you could create a site with the added personal touch that the cobalt system doesn't have. The cost is not proportional to the number of sites the group has as there will be a portion that is needed irrespective of the number of sites. The Kia international image is also at stake, so you would be limited to their corporate look.
Another thought, check the frequency of changes/updates. There could be too many to handle for your available time and reward. On the other hand if there are few, e.g. only new vehicles, it could be a bargain.