Each to their own, if you would like to get big power from a 1.4TSI, you would have to put a lot of effort, time, patience (and funds) into it.
Me personally, if I have the funds to modify a car so much that it would cost more than a Cupra in the first place, I would just get a Cupra (and remap it), and I'm sure this is the consensus of everyone here, the package is already 'ready made'...would be so much easier!
However, I believe you might be the type who like to do a big project...like to be rewarded for hard work well done and a sense of acomplishment, and the type who like to do things because they are hard and not because they are easy (would be just easier to get a Cupra), do not let other discourage you, but just be aware that you would need to change A LOT, and if you change some components and not others, things may go 'kaboom!' literally!
Can it be done, if an
Ibiza with a 1.4TSI (non Cupra different generation) can do it, yes...it's lot of work though, you would probably have to change a lot to get an have a look here (to get you an idea/started):
https://www.seatcupra.net/forums/threads/seat-ibiza-fr-1-4-tsi-stage-3-469bhp-560nm.425929/