Sorry Till! I miss read the post thinking it was your post verses Dan's. After reading your filters I do see your point, I appologize.
I cannot find any flaws in your web[id] filter.
I have your same fear with my filter. If it is done correctly it would be hard to allow others to expand on or allow updates. I would be time consuming to force a check for every revision of the cms's we support. However, would it be unwise to provide trusted cms packages on the website?
Complete judgement call on your part.
However, my concern was with $value. I believe holes can be punched through the filters for $value. I need to read the php documentation or ask a friend to make sure about this. But, I beleive escapseshellcmd() in php only filters single characters not double
% will be kicked out but
%% will return only a single %