It is permissible for the Muhrim to stipulate a condition for exiting Ihram because of sickness and the like Sahih Muslim 1208 b

Sahih Muslim 1208b
Arabic hadith text
حَدَّثَنَا هَارُونُ بْنُ عَبْدِ اللَّهِ، حَدَّثَنَا أَبُو دَاوُدَ الطَّيَالِسِيُّ، حَدَّثَنَا حَبِيبُ بْنُ يَزِيدَ، عَنْ عَمْرِو بْنِ هَرِمٍ، عَنْ سَعِيدِ بْنِ جُبَيْرٍ، وَعِكْرِمَةَ، عَنِ ابْنِ عَبَّاسٍ، رضى الله عنهما أَنَّ ضُبَاعَةَ، أَرَادَتِ الْحَجَّفَأَمَرَهَا النَّبِيُّ صلى الله عليه وسلم أَنْ تَشْتَرِطَ فَفَعَلَتْ ذَلِكَ عَنْ أَمْرِ رَسُولِ اللَّهِ صلى الله عليه وسلم
Translation

Ibn `Abbas (Allah be pleased with him) reported that Duba`a intended to perform Hajj, and the Messenger of Allah (ﷺ) commanded her (to enter into the state of Ihram) with condition. She did it in compliance with the command of Allah's Apostle (ﷺ).