理论上的英文

从理论上来说，看来是可行的。It seems to work in theory.

类似 generally speaking 应该是theoretically speaking,it seems could be works.

那我直接复制你的英文翻译然后修改就好了。Dear XXXX,For some unknown reasons, I haven't received your email yet. Could you please re-send me the email? Also, about the make up test（因为后面你用了take，所以我感觉take the test比较顺）, can I take it on Monday? Since, literally, students are able to change their subjects（换课不知道你指的是换专业吗还是？一般我们会用adjust curriculum schedule，就是调整课程表） during the first four weeks. It is very important for me to take another subject（美国还是用course这个词比较普遍，不知道你是发给哪个国家的教授？） this semester. Please consider this, thank you. (嗯这句话怪怪的我们好像不会这么说，你可以试试“I hope you can understand that the results of the makeup test is really vital for my study, if you allow me to take it on Monday I will be very grateful. Thank you very much! "）最后重启一段加上”Sincerely, 你的名字“ 就是一篇很好的邮件啦

重译版本：I haven't received your email. Could you please resend it to me?Regarding the make-up examination, is it possible for it to be scheduled on Monday? Because students can only reselect courses within the first four weeks, while it's very important for me to select a different course this semester.Thanks for your consideration!

in theory,it seems workable .

theoreticallyin reality/fact

It seems available in theory.