Getting back to the game and the OP, I think for me there are only two ways we can get all of our attackers/goalscorers in the team and maintain some semblance of central stength.
Firstly, we would have to drop Downing, and actually copy what Southampton did, and play a 4-2-3-1 with a tight "3" behind Sturridge:
Henderson would give us the ability to press, Lucas would give us the solidity in the middle, freeing Gerrard up to roam between the two and find his passes. Coutinho and Sturridge would have free reign to play as two Number 10's behind Sturridge, so we get the mobility we know is effective but with the added option of the directness to Sturridge. We also maintain our width through the fullbacks. Skrtel and Carragher could be interchangeable.
On the other hand, we could drop both Henderson and Downing, and play a 3-4-2-1:
This would give us the solidity in the central defence where we are vulnerable, and retain the mobility and the direct option up front, but it means we play with a midfield two. The alternative is to play Suarez and Sturridge as a front two, and Coutinho as part of the central midfield (3-4-1-2) and maintain the 3 in the middle that suits us, but means we can only get our width from the wingbacks, which could make our possession somewhat predictable.
There are solutions there, but I'm not sure Rodgers will look in that direction?
My preference would be to swap Henderson and Gerrard in the top one. When we actually win the ball, I think that would be far better for us. Plus I think Henderson's future role should be as a deeper playing CM. Still remember his performance as a RB. IMO he showed more qualities there than he has as an attacking player. I'd like to see him in a disciplined role, where he collects the ball and just passes it on to more creative players.
I don't like three at the back, but I certainly see your point about the second formation. It makes sense with the players we have. With Allen-Gerrard in CM, I would have liked to see that solution. To give us more stability in the middle. Now our center is like the wild west saloon doors. You push a little and it's an open route straight to the target.
Can someone explain to me the sudden need to have 'all of our attackers on the pitch'
I can't see a functional side which has Coutinho, Sturridge, Downing, Suarez and Gerrard in it I really can't - doesn't matter how you set them up the bottom line is that's half the outfield team with little or no 'off the ball' defensive ability; just don't see it
Worth thinking about. If we look at our team/squad, where are we going with it? What is our prefered 'system'? Take our signings (excluding Assaidi as I think he's a backup or an extra option), how do they fit together? Allen, Borini, Sturridge, Coutinho. Now add the obvious starters in Lucas, Gerrard and Suarez. What system do you play to fit them all in, or at least as many as possible? Has to be a 4-3-3 with wide men and a lone striker. Play Suarez as the second striker and there's no room for Allen, Rodgers' most expensive signing to date. But it also means, if we go 4-3-3 with Allen in there, that two of Suarez, Borini and Sturridge will have to play more on the wing.
Now it's easy to draw too many conclusions after a defeat, but where are we going with this? When I have my more sceptical days, I think we have a lot of (let be good) pieces that just don't fit together.