Any way to modify a definition in the locale on the fly?

I've got a plugin where I am rewriting the line on the discussions page, it works fine but:

public function DiscussionsController_AfterCountMeta_Handler(&$Sender) {
    $Discussion = $Sender->EventArguments['Discussion'];
    $First = UserBuilder($Discussion, 'First');
    $Last = UserBuilder($Discussion, 'Last');

    if ($Discussion->LastCommentID != '') {
        echo '<span class="LastCommentBy">'.sprintf(T(' %1$s'), UserAnchor($First)).'</span>';
        echo '<span class="AuthorDate">'.Gdn_Format::Date($Discussion->FirstDate).'</span>';
        echo '<span class="LastCommentBy">'.sprintf(T('| Recent %1$s'), UserAnchor($Last)).'</span>';

    } else {
        echo '<span class="LastCommentBy">'.sprintf(T(' Started by %1$s'), UserAnchor($First)).'</span>';
    }
    return;
}

public function CategoriesController_DiscussionMeta_Handler(&$Sender) {
    $this->DiscussionsController_DiscussionMeta_Handler($Sender);
}

e.g.
 5 comments Most recent by Lincoln March 7

to: 
4 comments  Peregrine  February 18| Recent Lincoln March 7

where
"Peregrine and February 18" are the original author of discussion and start date of discussion
and "Recent Lincoln" replaces "Most recent by Lincoln".

I've manged to do this by creating a new locale that changes the definitions like so,
to remove the old definitions.

$Definition['Most recent by %1$s']='';
$Definition['Started by %1$s']='';

My question is there a way to do one of two things
1) change the definitions from the plugin on the fly.
or
2) write the definitions from the plugin itself without having to create a new locale just for two definitions.

Currently it is a two step processor.

Another entirely different option - I could also do some improvisation with jquery and change the text and html in the class, but it doesn't seem like the ideal way to go.