I think what you describe is a good example of the type of workflows where Agenda definitely can be a hub for, however it will also require some trial and error in findings the perfect way for it to work well. There are already a number of threads in the Talk section of Agenda that go into various ways how you can tackle this, for instance this recent one: Suggested solution for my workflow with lots of projects and actionable items?
There are some features on our to-do list for future updates, like the ability to create overviews of unchecked to-do items, but there are alternatives you can try. Two things that immediately come to mind, are to make one project per client and use pinned notes at the top for a “current status and overview”, where for example you could put those follow ups. You could even assign a date or link to a (new or existing) calendar event as a way to concretise the next deadline you set). Have a look at this post which goes into a number of examples: Copy-and-Paste 2.0 – How Templates Make a World of Difference
Second, you might be able to instead of reminders, make much better use of tags, and in particular due tags or tags with parameters, for which you can make overviews.
It’s all a matter of experimenting and fine-tuning I’d say!