Of course, it is just impossible that Madueke replaces Saka. Saka will be always the main option for the right winger, meanwhile Martinelli is the main player in the left winger. Madueke probably becomes the substituted player of these players only. Madueke must accept that he may not play regularly as the starter. He must already realize this condition before he accepted Arsenal offer.
You are right about all this things you said about Madueke because the club cannot give him a regular opportunity so he should be taking anytime they put him in a good fate because he cannot outshine those two players, in Arsenal Saka is irreplaceable so long as he remains on that club, his replaceable can only work when he is ready to leave the club if not Saka has found home on that position and is whenever the coach like he will put Madueke, although the guy is a talented one but were he found himself is weigh past him.