The short and sweet suggestion:
When updating a username/password for a site and LastPass identifies more than one potential match in the drop down menu that asks you if you want to update; allow users to select multiple potential matches and update the username/password for all of those sites.
The Detailed Suggestion:
There are a couple of sites I use that LastPass has trouble identifying as the same same site and stores them as separate username/password combinations even though they are the same (this primarily occurs for my company's sites). Often when I go to sign into a page/application/etc for that site I am met with several sign in options and have to pick one to sign in and hope that the username/password is correct.
This is usually not a problem as even if there are multiple options, the username and password saved are usually the same. The issue comes into play for sites that require me to update my password (like my company). When I update my password LastPass is pretty good about identifying several different username/passwords that it thinks might need to updated, but it only allows me to update one of them. Then the next time I go to sign into one of the sites/applications LastPass again correctly identifies several sign in options it thinks tie to the site/application, but only one of them has the correct password.
I realize that the best way to handle this is to have LastPass identify those sites as the same in the first place, but I have been unable to get it to do that successfully. I have also tried using the 'equivalent site' without much luck. Adding the ability to update multiple sites at once when changing a password seems like a relatively easy way as a workaround to this issue.