Is this to be a short-term change intended for 1.6 or for the longer term?
You mention concerns so I suppose I should mention that I'm always concerned about accessibility changes that see removing tables as a primary goal rather than a side-effect of larger changes. Much like 'table-free web designs' that were in vogue a few years ago, it seems like a strangely focussed technical accomplishment to trumpet in the context of a big, fuzzy, ongoing user-experience challenge.
The fabulous, though slightly dated, dive into accessibility by Mark Pilgrim makes basically no mention of layout tables amongst its many recommendations, suggesting only that they be made to linearize properly and are given empty table summaries (see day 19: Using real table headers in particular the A very important note about layout tables section, and day 20: Providing a summary for tables, the layout tables: how to do it section).
Joe Clark's Building Accessible Websites, especially Chapter 10, Tables and Frames, comes out strongly against the demonisation of layout tables with comments such as:
Theyre not per se inaccessible. Theres a misconception that adaptive technology cannot read and understand tables. In fact, all major screen readers (on Windows, at least: OutSpoken on Macintosh is an exception) have specific commands for navigation inside tables. Since screen readers can also drive Braille displays, table-based layouts are accessible even to deaf-blind visitors. Layout tables pose surprisingly few access barriers.
I realize that the web has moved on since these things were written, and that CSS layouts have always been able to do some amazing things that Internet Explorer has finally caught up with, but I have to confess to some surprise at the focus on removing tables for accessibility reasons when there's so many other things to be done.