My A5 (A5.52 - 5.24 probably is smaller) executable is 800kb big. This is about 360kb more than A4. Now that can't be the reason.

What I want to say: You can use A5.24 as well. There are no disadvantages.

If they re-release A4... hell yes, why not. But I see no use in that.
About networking: A4 multiplayer was bugged and certainly has more problems running on 10 mbit than A5.