Here's "the system" for this year. Looks like it'll be especially unhelpful though: two thirds of the field are on the top two rungs! No horse gets a perfect score (unless there are some substantial odds changes for some of the runners).

Total	Name	Less than 8yo	Wgt < 57kg	Not a mare	<= $21 SP	< $16 in last	Wgtd < than in last	FS in last >= 10	Won Black Type	<=3L in last	<6 victories
9	ABSURDE	1	1	1	1	1	1	1	0	1	1
9	CLEVELAND	1	1	1	0	1	1	1	1	1	1
9	FUTURE HISTORY	1	1	1	1	1	1	1	1	1	0
9	GOLD TRIP	1	0	1	1	1	1	1	1	1	1
9	INTERPRETATION	1	1	1	0	1	1	1	1	1	1
9	MORE FELONS	1	1	1	0	1	1	1	1	1	1
9	SERPENTINE	1	1	1	0	1	1	1	1	1	1
8	ASHRUN	0	1	1	0	1	1	1	1	1	1
8	BREAKUP	1	1	1	1	1	0	1	1	0	1
8	KALAPOUR	1	1	1	0	1	1	0	1	1	1
8	LASTOTCHKA	1	1	0	1	1	1	0	1	1	1
8	SHERAZ	1	1	1	0	0	1	1	1	1	1
8	SOULCOMBE	1	1	1	1	1	0	1	1	0	1
8	VAUBAN	1	1	1	1	1	1	0	1	1	0
8	VOW AND DECLARE	0	1	1	0	1	1	1	1	1	1
8	WITHOUT A FIGHT	1	1	1	1	1	0	1	1	1	0
7	ALENQUER	1	1	1	0	0	1	1	1	0	1
7	DAQIANSWEET JUNIOR	1	1	1	0	1	1	0	1	1	0
7	MAGICAL LAGOON	1	1	0	0	0	1	1	1	1	1
7	MILITARY MISSION	1	1	1	0	1	1	0	1	1	0
7	VIRTUOUS CIRCLE	1	1	1	0	1	1	1	0	0	1
5	OKITA SOUSHI	1	1	1	0	0	0	1	0	0	1
5	RIGHT YOU ARE	1	1	1	0	0	0	1	1	0	0
4	TRUE MARVEL	0	1	1	0	0	1	1	0	0	0

You might have more luck with biorhythms! Breakup, Military Mission and Vauban will all be at their top physical rating on the day, according to that silliness

I've spent very little time looking at the race but Vauban, Gold Trip, Future History, and Breakup can be my guess at the first four.

For what it's worth (sadly these ratings don't have a great record on the Cup)

FLEM 7 - MELBOURNE CUP 3200M

RTG . ODDS . VALUE . HORSE
23.0 . $4.30 . $5.95 . 3 WITHOUT A FIGHT
23.0 . $4.30 . $5.95 . 5 VAUBAN
13.0 . $7.70 . $11.05 . 7 ABSURDE
10.5 . $9.50 . $13.75 . 1 GOLD TRIP
10.5 . $9.50 . $13.75 . 6 SOULCOMBE
6.5 . $15.40 . $22.60 . 9 VOW AND DECLARE
5.0 . $20.00 . $29.50 . 4 BREAKUP
5.0 . $20.00 . $29.50 . 15 LASTOTCHKA
4.0 . $25.00 . $37.00 . 20 MORE FELONS
4.0 . $25.00 . $37.00 . 21 FUTURE HISTORY
2.5 . $40.00 . $59.50 . 17 MILITARY MISSION
2.5 . $40.00 . $59.50 . 18 SERPENTINE
2.5 . $40.00 . $59.50 . 23 KALAPOUR
2.0 . $50.00 . $74.50 . 8 RIGHT YOU ARE
2.0 . $50.00 . $74.50 . 11 ASHRUN
2.0 . $50.00 . $74.50 . 13 OKITA SOUSHI
2.0 . $50.00 . $74.50 . 22 INTERPRETATION

CL/WT RTG: 3 WITHOUT A FIGHT
FORM RTG: 5 VAUBAN

Incredible dividend in the end for Without A Fight.