I played Shadow world as a player (lvl 25 Chaotic lord at the end of the campaign) and I saw some inspiration in the game system of Anima from Rolemaster(open ended roll, multiple bonuses to skills, spell taking more time to cast when stronger ...). but I also found some similarities in the world / background : battles of ancient powers changing the world geography, necromancy being a form of magic that destroys essence somewhat makes me think of the Unlife, Duk'Zarist having a perfect body and resistance to death and with great regeneration somewhat made me think of Lords of Essence, some Shajad/Beryl more or less resemble the Shadow world gods ...
Did some of you think about that? i'd really like to introduce some things from Shadow World (and as we know "something was forgotten", maybe millenia ago Gaïa was called Kulthea ... could be fun/dangerous if the players met Andraax!)

Absolutely! If you wanna incorporate things from other elements then go for it! Artists borrow from eachother and even more so of storytellers. I for example; have changed my Gaia world considerably and made it rather akin to a The Coldfire series by C.S. Friedman. I wanted even more contrast for the light and dark and so when it's nighttime in my world, shadows and other things enter the realm much more.