User blog comment:Stbk22/Possible Power up's/Techniques for then new group DxD/@comment-85.154.145.43-20140205161824/@comment-1359322-20140206010343

I don't think they would think about it like that Euclid's Boosted Gear was created using the remains of Issei's previous body, in a sense Euclid is using what's rightfully Issei, what's wrong with Issei taking it back. And if it serves as a power-up, then it's like killing 2 birds with one stone.

Also every member in Rias' team also rely on other people's power to improve themselves too. Rias' new move is an affect of Issei's Dragon power. Akeno's Raikoryuu is also because of Issei's Dragon power and the Fallen Angel mode is currently made possible by Azazel's bracelet. Yuuto's Sword of Betrayer is done by fusing the Souls of his deceased friends with his Sacred Gear and the Glory Drag Trooper was made possible with training with Issei. Koneko managed to obtain the "Shirone mode" because of her training with Kuroka. Asia is depending on Fafnir. Xenovia is practically learning how to master her Ex-Durandal with help of others. Rossweisse's actually went back to Valhala to train. And finally Gasper who managed to obtain his Forbidden Invade Balor the Beast with Valerie's indirect action of implanting a part of Balor's will into his SG.

So i don't see any problem on Issei relying on others.