but I can't easily report against that SLA  I have to trick the reporting system by using a field or make use the subject field.

Why can't we just report against the SLA?  

we don't use 1 sla for all tickets. we have many specific issues all of which need different SLA's
which comes to my next request why do SLA's need to be so general  why can't they be specific
under tasks i can select an SLA  why not have this for all tickets?