"There will not be a full-blooded equal car arrangement from day one, it cannot be," he added, but he did not rule out either fielding a hybrid chassis or a different car altogether.
The main complication for Prodrive is the ambiguity of the 'customer car' rules for 2008.
Williams recently wrote a letter of protest to the FIA, and Max Mosley has referred the matter of Prodrive's legality to the Court of Appeal for a hearing later in October.
But even though a new Concorde Agreement for 2008 is not yet in sight, Richards insists that Prodrive remains "committed to participating in formula one".
"In the meantime, we will consider all our alternative options for next season," he added. (GMM)