Yes, but it's going to need a lot of work.
I suggest you read the help file in the following areas:
/window
$strip
While the /window command does state a custom window, most of the /window commands will work with channel windows as well, and in the same manner.
Regarding the search, you would have to use $fline to find the line.
Please note that it's not possible for you to take someone else's text, then change it, before having it be processed via the server and displayed on everyone else's clients (exception being if the message is sent to you via pm/query first, then you send the altered message to the channel.)
