On the theoretical part, sure, but feasibility is a reasonable aspect of the discussion.
You're suggesting a sequence like this, I think:
a) Blast at basic strength. Bought as Constant. Attack hits, does its base damage.
b) next phase, Aid to Blast. It automatically hits because the target of the Aid is Self. This adds points to the ongoing Blast so now it's stronger.
From a rules standpoint, it's technically legal I suppose, but it's tending to give more Effect than it costs. If the Blast has just Constant and 1/2 End, each +1d6 would be 8.75 points, which means 2d or 2 1/2 d Aid. Aid gets the wonkin' big Self Only mod. You could add Constant to just let the Blast grow forever, and now, say, just Dodge to your heart's content...or, you could eschew the Constant and take multiple actions to increase the Blast to the limit of your Aid. Assume the latter; Now. given the slow fade rate, you may well be able to skip the Reduced END on the Aid. It's less necessary because you know it's guaranteed to be effective...there's no chance it'll be wasted. So you could buy 9d6 Aid for 27 points. One use is adding 31 points onto the Blast, for multiple rounds. That's gonna be 3 to 4 d6 mostly, depending on the roll, and a second use is likely to cap it out at +6d6.
Now, to be sure, this is taking time, and time and actions are the currency of combat. And the points for the Blast and the Aid have to be distinct as they both have to be in use. So I might allow it, if the concept and full details of the implementation work for me.