No cap is not an option if you expect bankers to play the game, although that forces SS on everyone so might be entertaining 
The cap is there to make the game playable beyond a single attack surely? otherwise you would just jump one guy with all resources he would crush the entire enemy team and its all done.
That’s true if we are entirely unable to make other changes. However, that isn’t the case:
Or simply put: what is the cap trying to achieve, and can we achieve it through some other mechanism?
We know the cap causes problems, so let’s replace it with something else. What, exactly? Well, that’s why we’re using our collective brain power. 
Alternatively, we leave the cap is as. Regardless, we can’t spin our wheels discussing theoreticals forever. If we don’t have a solid recommendation on how to fix the problem you guys are facing, then it will go out as is.
Our options at this moment:
Leave the cap as it stands
Adjust the the cap, including the option of adjusting it to 100% (removing it)
Replace the cap with something else that serves the same purpose but without causing the same problems
We have about 4 weeks to figure it out. If we can’t, we’ll go with either #1 or #2. Either way, we will be pushing this feature.
As a reminder, we can and will iterate on this feature after it is initially pushed. We will take the feedback and improve upon it round after around. The code was rebuilt in a way specifically to facilitate that kind of continual improvement.
What we shouldn’t do, is let a desire for perfection hold us back from deploying it.
We will try our best to balance things, but if we don’t have enough collective resources to figure out all of the solutions before we release this feature, then we will figure them out after.
Give them the third best to go on with; the second best comes too late, the best never comes.
It sounds like leaving the cap and having the cap as it is isn’t an option.
Maybe have a “retreat” threshold? For example if I attack a portalled planet with 10m droids and the banker has 5m droids, the battle logic applies until one side loses x percent of their forces? And once that threshold is triggered, the attacker takes the planet and the battle stops there. The same would apply if the attacker has the smaller fleet, they would lose x% and a retreat would trigger and the battle stops there and defender wins.
Or even letting the empire select their retreat threshold would be interesting. Some may want to defend with 100% all or nothing type of defense, while others would rather give up a planet after losing 10%.
And with offense, some may want to kamikaze and do as much damage as possible, while others would prefer to give up after a 10% loss or so and retreat from battle.
Yeeaaah now we’re talkin. DA had a similar take in the other thread:
We already have nw % thresholds that determine building losses, a loss-based retreat mechanism would fit very well alongside that general concept.
Ya I think this is the way to go … and letting the empires select their retreat threshold opens up a whole new avenue of strategy.
I like that idea, on top of def % introduction and attribute changes and you’re well on your way I think.