Is it possible to play the original and HoF campaigns within Tribes of the East?

Solution 1:

There's a really easy unofficial add-on made to integrate the H5/HoF campaigns in TotE here: http://www.heroes-fr.com/pages_en/original_campaigns.php

All you need to do is download Campaign and Text files (plus Cutscenes and Dialog if you want them) and put them in your ToE UserMODs folder. No ToE files need to be changed, patched or overwritten. More detailed instructions are on the link above.

The standalone format they released the expansions in really annoyed me too. Just remember when playing the old campaigns, the AI is equally capable of using the new creatures and everything else!