I think party should not exist. His ability should be his and his alone.

No joke, but this is kind of getting really messed up.

my brain is fried from reading your stupid grammar hurry up and come back to fix all of the errors I can't even form words properly because of it.

Here's an advise from me use grammarly and don't repeatedly use because all the time, also your wordings needs improvement. This is coming from the guy who scores badly in English.

So he could... Trace... Excalibur... RAPIDLY!?HAHAHAHAHAHAHAHA HAHAHAHAHAHAHAHA

Fun fact Rho aiasis a anagram for Ria's a ho HAHAHAJAJAHAH
DHFHNVSFMDKDNDJDJ PENGUIN PENIS

I still ship Shirou and Saber oi!

Man, he's basically becoming EMIYA with the way he's going on.

Man, I hope you don't go fucking full-blown Harem with girls falling left and right for our MC without any reasonable fucking questions just like in the anime.

Maybe the effects of having a Gate of Babylon-like is making him a douchebag? xD

Man, this Issei is really OOC, not that I don't like his personality but even though he is not perverted his character is completely different.
You should have made him OC

So genius gets triggered several times, makes a show of power, gives them several gifts that are clearly overkill for no reason, then gets surprised it backfires? let's just remove 4 or 5 digits of intelligence from that good ol triple digit hes sporting.

He needs a gucking Cha stat ASAP! Please let Draig open that stat!

Please continue or do a separate rewrite please since I like this version as well.

I really hope this gets better from here because so far it's just been lumping a bunch of skills that look cool onto Issei without any sort of foundation