If you try to add new creatures in already started game it wont work, you have to add all files concerning some unit, and then start new game so it appears in it. Same as for difficulty lvl you can`t change it mid game, you have to start anew.
Try coping all those files you think are needed and start new game, Maelstrom should appear in main castle on Debir island (its made this way in RSE mod) so you`ll know did you succeed. Because all this mixing of files is reason i stop trying to add champion in my RSE.
In my previous post i listed all files i found mentioning champion unit 5 files just for champion, and 7 more that contain something about units in general : champion.atom , champion.png , army_champion.atom , champion.bma , champion_diff , colision_champion.cms , addon_unit_features.lua , eng_units.lng , special_attacks.lua , special_params.txt , unit_features.lua , unit_morale.lua
Other problem with importing champion in RSE or regular red sands, is his special skills battle spirit that gives him bonus att/def with every hit on/against him and in red sands all humans have passive skill battle spirit that give them % for 1 more turn after acting in that battle round. So i had problem finding all battle spirit strings for champion in `adventure mod`, and renaming them so they wouldn`t conflict with battle spirit talent of all humans in `red sands` , all in all to much problems for importing 1 unit ( bladeking77 did great job with creating new units) but had bad luck naming it`s passive talent same as red sands crew so it`s big trouble to add champion in newer mods.
As for azure dragon it`s interesting unit to play, only if you set it possible to resurrect by inquisitor/demonolog like any other unit in game. In original settings it`s completely magic imune but in difference to black dragon (who are possible to revive inquisitior) you cant keep them alive at all
and with their magic scales they can be great tanks for mage hero class who concentrate on spell dmg.