保送生有多种翻译：
students by recommendation
recommended student
School-sponsored Students
以下是成绩优秀的保送生
elite students
talented students
scholars
我的建议：
"跨专业保送生" cross-disciplined school-sponsored students
是的，interdisciplinary比cross-disciplined通用。interdisciplinary recommended student感觉很好啊，或许试试看调换一下词，改为recommended interdisciplinary student，因为interdisciplinary修饰student比修饰recommended student更为顺畅，不过还要看哪一个是主语的重心。