I am a non-expert in this field, just have a layman's interest in the subject. Has anyone ever considered the possibility of magnetic monopoles (one positive and one negative charge) being confined together like quarks, and hence that could be the reason monopoles have never been observed? At the macro level the total magnetic charge would always be zero due to the charges being tightly bound.
The answer to your question, is yes, it has indeed been considered. The bound state has even been given a name "monopolium". Here is a paper discussing prospects for detection and production.
I should add the caveat that they're not strictly, in your words "confined together like quarks". You could separate them if you input enough energy, unlike the quark-gluon case.