Some ideas for Endor battle:

Ideas that have been mentioned before:

(1) make the rebel fleet MUCH larger (hundreds of ships), but with smaller ships that are faster than the SDs. Maybe instead of one singular fleet, there are multiple fleets that are enmassing and they all jump in at the same time (you could show said extra battle fleets jump in on the left and right side of the DS/Endor when they come out of hyperspace). You could add a throw away line about remote controlled ships, ala the kamikaze transports,

(2) which would account for the massive damages the imperial fleet takes. Ady (or anyone for that matter): reference the battle of Jutland or the battle at Okinawa - the latter of which was bloody as hell due to all of the kamikaze pilots ramming into US carriers.

(3) I don't know how, but I would either do something with Piett along the lines of Bingo's suggestions and have him do something heroic - if so, there would have to be a reason. Maybe the Emperor goes nuts to a degree and has the DS laser do a swiping arc and starts to destroy both rebel and imperial ships. Earlier in JEDI, someone could take one of the scenes from EMPIRE where Piett looks uneasy or upset and work it in to show he already has his doubts about what is going on. Seeing the Emperor start to destroy everything just to get at the rebels could tip him over to give the order to attack the Death Star even if it is just to save his fleet.

I would still like to see something along the line of Piett shaking hands with one of the rebel generals at the teddy bear picnic to signify a true ending where the Empire COULD become a new republic. Whether than means showing Piett escape, or having him (A) fire at the shield generator, which destroys it, then (B) rams the Executor into the DS, which takes out enough guns that the fighters have a clear path ahead to get into it. In fact, how crazy would it be to see 2 TIE interceptors escorting the Falcon to the reactor (on orders from Piett)?

(4) for the general battle (before Piett gets his chance for redemption), I would also show the TIE interceptors taking a few hits before being destroyed (as they have new shields ala the X-wings, to show the Empire can adapt too) as well as get some more kills to show that the pilots have some actual skill. I would also show an X-wing bounce around inside the DS pathway to the reactor as opposed to a more nimble TIE, whose pilot could possibly use his computer to input a trajectory, being that he could access a map of the DS (whereas the Falcon and co may not - unless there was a detailed map in the captured plans).

(5) EXECUTOR destruction: either Piett ramming into the Death Star per above, or have multiple kamikazi ships ram into it and overwhelm it with massive destruction. I do like Vaderios' idea of having the Executor fire a barrage and maybe wiping out a good 10 or 20 mid-sized rebel ships in that one volley.