The main issue is no one here who can do something like this wants to waste 1-4 (or more) hours building it. MVT wants an ignore button and you want a user list and there are probably some other requests floating around, but none of them have been cool enough or useful enough to me to get me to sit down and build something. Honestly, I'd have a lot more fun taking the current board software and paring it down to remove all the stupid extra features.
If you want a feature, your best bet is to either find a package that someone has already created, or create one yourself. Then even with our hacked up board it wouldn't take more than 30-60 minutes to set up. If you had some mind-blowing amazing new thing that wouldn't take a ton of work, I'm sure someone would do it...but most of the things people have asked for have a trivial value but require a lot of work to implement.
The users online list is based on a list of people online in the last 15 minutes. After 15 minutes, they fall out of the list so they aren't reported on the board anymore.
If you want to use that structure to see who was online in the last 24 hours, first you'll have to get that file to keep names in a list for a full 24 hours, then you'll have to fix the 15 minute one to only show people from the last 15 minutes, then add something to display the list of names in the last 24 hours.
The alternative is to develop a routine that checks the last online time of every member, then displays those whose time is within the last 24 hours. This might be easier...
Anyway, if you really want it the best way is to do it yourself

. All the files you'll need to see are available here:
http://www.yabbforum.com/archives.php