So this is an analysis of the servants and their relationships with their masters in order to determine the ones who I think would have actually won the holy grail.

So let's start with caster.
Caster main advantage in the war, is her Master and her servant assassin, but she is ultimately the one with the least chance of being able to win the war, first while her magic is incredible most of the servants their can easily Handel her magic, with archer pretty having one shot her. And while assassin is definitely skilled, it's unlikely he could survive a hit from a noble phantasm, a while rule breaker might seem like a way to even odds, it relies on her being able to get close enough to her oppenent to actually use it, and the one time she was able to do so was with Emiya useing a command seal on saber to stop her, other wise caster probably would have died.

So so next is saber.
Saber is an extremely warrior able to go toe to toe with berserker, however becuase her master is Emiya is doubtful she actually able to win the war, while she does have a powerful Nobel phanatsm useing it would leaves her with so little mana that she would become incapacitated until either she enters a better a contract to help replenish her mana, or that scene occurs, either way without help shed likely towards the middle or climax of the war likely it be becuase emiyas stupidly. Or by the hands lancer or berserker. So while she is powerful she just to much handicap to let her live to the end of the war, but don't mistake that for no chance at all since if she can enter a contract with say rin or a better Mage she could probable you win the war, since shed wouldn't be limited to only one use of Excalibur, or she could get extremely lucky like she does in the vanilla route of fate. Thou without one or both of those two things happening she probably wouldn't live past ten climax of the war.

So so next is rider.
Riders speed, combined with her two noble phanatsm said gives her a decant chance of winning the holy grail war, if it wasn't for the fact that her phsudoe master is Shinji since his arrogance will most likely get her killed in the climax of the war, thou if sukura remains her master shed actually have a good chance of winning the war, since her speed/agility is relieved good, and her first NP being able to restrict movement of her oponent, and then combine that belephorine you got a good line up(an OP) of NPs, that would be very difficult to survive, since if she plays her cards right, she could depending on who the last servant simply finish them off by useing her first Np followed by bellophorone. But alas if her master is Shinji I doubt she even makes to the climax.

Lancer is one who has the one of the best chances of winning, as he has riduluse speed, good stats, a pretty good NP, great skill and the only thing holding him back is kotomine, however since I'm going with no outside intervention(ahem Gilgamesh) he'd play a huge role the climax and would probably be part of the final battle, it just comes down weather or not berserker lives to the end. As if his last oppenent ends up being berserker he's pretty much screwed, since lancer has no real way to kill him becuase of Gods hand, and honestly I really doubt that berserker is not going to make it the end.

archer has a really good chance of winning, since he has the skills and abilities to at least hold his own against the vast majority of the servants who would be left, his varied weaponry, and thus skill will make it hard for the other servants to kill him, combine that with eye of mind, and skills like Crain wing which basically creates an undodgeable flurry of attacks, and his ability to turn NP into and creat broken NPs, are likely going to let him to live to the final battle. As he see the final battle as pretty much, being archer, berserker, lancer, with saber ding becuase of her handicap likely at the hands of berserker,r medusas dining becuase of shinjis arrogance, caster just really can't win at all against any of the other servants. And I see archer just waiting from a distance for berserker to kill lancer, since I really don't think Ilya will go after archer simply becuase lancer, and her belief in berserkers abilities will probably cause her to see archer as something she can wait and just take the closer enemy, lancer. The battle between the. Will be based on how many lives he can take,mthemminum he needs to take from berserker will be at least three, which I can see happening with some difficulty, the biggest thing is that archer already his chant ready so he can immediantly take berserker into UBW, and he'll need to take the rest of berserker lives, something not beyond archer skills but is not going be to be an easy feat.

So so here's how the progression of the holy grail war going.
I see caster, and their for assassin dieting in the begging of the war, maybe a day or two berg ore the climax, or death probably being caused by her desperation leading her to do something drastic, ultimately ending in her demise, I see the a couple of little battles her and their between the rest of the servants, the climax will probably start with the death of rider by the hands of lancer or saber, the climax will then be all out battle between saber and berserker with archer possible adding support, or just watching the battle take place from a distance, lancer will likely be near by hoping to duel saber, and then after battle were berserker probably has lost a couple lives by this, probably about two or three, killing lancer by illy as command, and then the final battle will be between archer and berserker, and the battle will probably be less decided by them, and more by the actions of their masters, but I see a very close knit battle with no clear indicator as to who will win.

This is just how I see it happening, so please do not be rude.