There is zero benefit in having the sheet number tied to the discipline. If you have an electrical drawing E-101 you would have to use discipline labeled E and which you would designate for electrical. If you also have a structural steel erection drawing that is labeled E-01 you can only assign it to discipline E which is electrical. The only way around this is to change the drawing number i.e. ER-01 to allow for a new discipline 'Steel Erection Drawings" to be created. By doing this, the drawing number in ACC and the actual drawing number do not match. It would be fine to have the disciplines labeled E for electrical and ER for erection but have the ability to assign these to whatever drawing you want. - E for electrical and ER for Erection Drawings.
The work around would be to use drawing tags but this does not allow you to custom organize the sheet order which is a huge benefit to disciplines.