I have done a lot of mixed breeding over the last 10 years. Here's what I've learned from my experiences.
First be clear in your goals. If you change them you will muddy up your line.
To start a project like this, I find it easier to choose a variety of pure hens and have a standard purebred rooster. It alleviates a lot of the unknown at the beginning you would get breeding mixes to mixes. You can control your variety with the pure mixes through choosing the hen's eggs you want to set. I've controlled my line so that I can look at the hen's plummage and know her heritage for blue, green, or brown eggs.
If you have two roosters, you will only want those hens available to the rooster you want to improve that hen's line.
In my experience, typically the rooster and hen combine to create a body size that averages the two. Egg laying is also an average between the two. If you want to increase body size, choose a heavier breed to place over a good layer. You will get decent layer with decent body size. If you want better laying, place a prolific layer over a heavier decent layer. Again, you will average the size and the egg laying between the parents with the prolific genes bolstering the overall laying quite a bit. Depending on the variance of the parents, you will scale up or down in your desired direction.
Since you stated you are wanting to go with a good mix of eggs and meat, I would skip the Cochin Bantam/Pekin and Silkie. They scale the whole line down for both egg and body for numerous generations. If you want to instill some good brooding hens in your flock, with 3/4 size eggs and body, that aren't very good for eating, then that could be a choice to add plummage variety, a larger broody body that can sit more eggs, and install a broody pen (which I have personally done)....but not your original stated goals for decent egg and body.
Your EE roosters are already mixed, so that will definitely add some unknown results (see first paragraph that starting with purebreds saves a lot of breeding headache). They will keep blue shells 50% of the time (if they are really EE's and have at least 1 blue shell gene...not always true in hatchery stock). They should be pretty middle of the road for gene in laying and meat, though they aren't typically very heavy meat birds. Place them over the Orp to increase body size of the EE line. You will likely stay middle laying. Place them over Leghorn types, or your Australorp, and you will get good layers, but not particularly good eating carcass with the Leghorn. The Australorp ( I think you said blue?) will likely produce 50% black and 50% blue depending upon the EE colors. You'll probably get some secondary bleed through depending on the EE secondary pattern.
Plummage is a bit trickier. Red base works wonderfully well as a pallet when adding lacing and patterning from the other parent. Buff can create some interesting secondary colors. You will want to get familiar with the genetics calculator and spend time making color comparisons. (See link below). Stay away from dominant white (White Leghorns) and black solids as those tend to be very hard to breed out. They tend to dominant all patterns and colors. (In my experience).
Barring can create sex links if your male is barred and your female is not. I've worked with California Grey, Rhodebar and Cream Legbar lines to success, with some interesting hybrids.
I really love my Barnevelders which are good tempered and produce very lovely gold lacing. The lacing breeds through with different secondary patterns by 2nd Gen...you get incomplete lacing with one laced/one not first gen. Again, spend time on the genetic calculator and work with pure breeds to set your pallets.
If you are serious about raising birds that are truly dual purpose, look at Buckeyes. Breed them back to RIR and you increase their laying and keep the body type.
Just some random thoughts from my experiences.
LofMc
Genetic Calculator
https://www.breedbook.org/?action=geneticscalculator&tab=CHICKEN