Changes in display of batch data entry form in 4.6.x
From UI perspective, it is not currently possible to include an email in the select box. Some code changes need to be done.

I was just skimming the code of Common.js file where this functionality seems to be handled.

I guess the formatSelection function is the one which returns to what is seen after the selection of the contacts from the dropdown. You can make a change here to include the email to be concatenated to the name. Something like:

var email = (row.extra.email !== '' ? ' - ' + row.extra.email + ' ' : '');


and then add this to the label.

Well, modification in this file may not be recommended  as changes done here are too core and may affect some other functionality elsewhere. This file is called in almost all the pages of CiviCRM and hence this change would affect all the dropdown present in it.