2 localizations inside a WordPress theme

Technically, this is possible. You can load as many language files as you want:

load_theme_textdomain( 'text_domain_1', get_template_directory() . '/languages/td1' ) );
load_theme_textdomain( 'text_domain_2', get_template_directory() . '/languages/td2' ) );

In terms of performance it may be useful if want to separate front-end and back-end translations.

But it is the wrong solution if do this to manage plugin code that you have moved into a theme. For example the notorious contact form, shortcodes or a dashboard widget – these parts should be handled by real plugins.

TL;DR: It depends on the problem you want to solve.