No, you could. You just have to state it in the Technique description. Otherwise, me being a GM with a lot of systems to watch over will be like "Okay, it's an attack type technique that means all effects go on the Target," and miss that Jane is boosting herself while attacking someone else.
Also, note that if you are casting an additional Technique on yourself, the boost will be only the quartered amount of the secondary slot + your base stat. So it might not be a huge amount.