The bigger fleet will always have an advantage over a smaller fleet by purely having reserves that the smaller fleet does not
And deployment points are one of those resources. One of the most important ones, in fact, since ships outside the battlefield don't contribute in any way.
The bigger fleet reinforcements has to crawl to the frontlines, so do the smaller fleet reinforcements, so what is the problem? Why are you operating under the assumption that you don't lose a single ship? Equal deployment points preventing an initial cascading success problem is the point.
This happens very often to me, when I'm outnumbered. And you ask for disadvantaging the enemy further.
I lose ships from time to time, but those aren't very meaningful events. If I'm being pushed back, then my reinforcements take less time to arrive to the battlefield. If I gain advantage, then the enemy doesn't retreat towards the top and regroup, instead trying to make reinforcements come to the initial wave. This leaves both forces overextended and an easy setup for defeat in detail.
I think you are overlooking the difference between fighting one big wave and several smaller ones. In the former case, you have to defeat them all at once, while in the latter, you can either defeat the smaller initial wave quickly, where you have more ships proportionally, then move to the reinforcements, maintaining local superiority, despite being outnumbered; or you can encircle or distract the initial wave, then slowly chip at both the main force and the reinforcements (where the main force has some chance at defeating you, but reinforcements are completely hopeless).