Hi
The release schedule is still being worked on, and involves a number of boring factors, but it is unlikely we will have all of the army lists available on day 1, However there will be a number of lists available from the start. We will also include a pair of compatible army lists in the rulebook so people can have a try. We have taken this decision, as we don??™t want to delay release till all of the army lists are available.
So far as rebasing is concerned we are very aware and conscious that having to rebase your existing armies would not be welcome, whichever rule set you have been using. So we will aim to avoid this.
The rules will cater for both 15mm and 25/28mm scales and I see no reason why 10mm would not work as well, just as long as you and your opponent use the same 
 
We very much believe that all of us who are interested in this period and wargaming in general have a great deal in common whichever rule set you have been using and we hope to build on this. For example we will shortly be calling for Beta testers to take part in a closed Beta testing programme and we hope that this will attract players from all areas of the hobby.
The rules are already at a fairly advanced state so we will be calling for volunteers pretty soon.
The Beta testing programme will be managed similarly to our already established procedures for computer games.
Best Regards
JDM