The thing is, the current code base grew out of a prototype that didn't have that much of a design. Well, it had a design but, in my opinion, it has turned to be a bad design. I couldn't imagine that we could hit the bottlenecks (speed) and user-interface issues (for example, the huge difficulties that involve debugging a failing test case) that we are hitting. So...
IT IS TIME FOR A CHANGE!!!
I'm currently working on a written specification of what ATF will look like, hopefully, in the not-so-distant future. It will take a while to get there, but with enough effort, we soon will. And life will be better. And no, I'm not talking about a from-scratch rewrite; that'd only hurt the project. I plan to take incremental and safe steps, keeping the code base running all the time, but I will do a major face-lift of everything. (I wish I could say "we" instead of "I" here. But not there yet.)
Why am I writing a specification, you ask? Well, because that forces me (or ANY developer) to think how I want the thing to look like and to decide, exactly, on what the design will be, which technologies will be used, which languages will be involved and in what components, etc. And no, I'm not talking of a class model design; I'm just talking about the main design of the whole picture, which is quite hard by itself. Plus having a spec will allow me to show it to you before I start coding and you will say "oh, wonderful, this new design sucks so much that I'm not going to bother with the new version". Or maybe hell will freeze and you will think, "mmm, this looks interesting, maybe it will solve these issues I'm having as regards speed, ease of debugging and ease of use".
Anyway, I hope to have a draft "soon" and to hear any of the two possible comments as a result!
Edit (July 29th): Alright, I have uploaded an extremely preliminary copy of the specification just so that you can see where my current ideas are headed. Expect many more changes to this document, so don't pay too much attention to the tiny details (most of which aren't there anyway yet).