---------------------------------
<form action="$Env{"CGIHandle"}" method="post" name="bulk">
 <input type="hidden" name="Action" value="AgentTicketBulk">
 <input type="hidden" name="Subaction" value="">
 <input type="hidden" name="Queue" value="">
 <input type="hidden" name="State" value="">
 <input type="hidden" name="ArticleType" value="">
 <input type="hidden" name="Subject" value="">
 <input type="hidden" name="Body" value="">
 <input type="hidden" name="TicketID1" value="">
[..skipping these lines..]
 <input type="hidden" name="TicketID29" value="">
</form>
<!-- end NavigationBar -->
#-----------------------8><------------------------------------

...this is part 1 of the (technical) reason why the number of tickets
used for bulk feature is restricted.

Part 2 can be found in  Kernel::Modules::AgentTicketBulk in sub Run,
which will handle at most 30 bulk ticket ids:

#-----------------------8><------------------------------------
foreach (1..30) {
   if ($Self->{ParamObject}->GetParam(Param => "TicketID$_")) {
       push (
           @TicketIDs,
           $Self->{ParamObject}->GetParam(Param => "TicketID$_")
       );
   }
}
#-----------------------8><------------------------------------


In order to get bulk action for 100 tickets, you'll need to add the
fields to the "bulk"-HTML-form (part 1) _AND_ extend the loop in sub Run
in Kernel::Modules::AgentTicketBulk to 100 - then it SHOULD work - I
haven't tried it yet.
Maybe you'll find a sophisticated search profile which fits your needs.
But this is to specific for a remote advice.