I'm not sure I totally buy the thing about the 5 gaited ASBs... I have one of those, she was never formally trained, but her lateral tendencies make her a difficult sell for dressage, and her tendency to change footfalls if she comes off balance can be a challenge to ride in hunters too. She has passed it on, at least once, to a non-purebred foal at that (was a Warmblood cross). It has altered my plan of breeding her... In my area gaited horses are almost automatically "trail horses". So going strong 5 gaited lines might work in getting more bone, depending on what you want to do, but the "ability" to gait comes with movement less desireable for some disiciplines. (And for the record, yes, my mare does walk, trot, canter... We have also been working on a slow gait - she will rack on her own (ugly as all heck because we have no clue what we're doing) if she gets wildly off balance in a canter.). I still do dressage with her, but she is just more of a challenge for that disicipline, as it looks for purity of gaits (just easier to get from a horse who doesn't have extra "gears")
The outcrossing really depends on what you do and where you are too. If I were in an area where Saddlebreds were better known, I'd be way more likely to stay purebred than any outcross... But, in my area the breed is almost unknown, and while they might have the talent and ability of other breeds in any given discipline, they are a hard sell as a purebred.
I had a lovely gelding I just sold. This horse had eventer written all over him...trainers, coaches and other riders all agreed... But Trying to get those sport riders out to look at him without trying to quibble on price (a price any of them would have paid for an equal (or lesser) quality TB ) was impossible. In the end I sold him to a lady who just plain loved him for him, which, while I'm glad he is well loved... It's a shame in my mind, he could've done very very well in Pony Club, or even open divisions.
Interestingly enough, around me, Saddlebred crosses are "accepted"... Maybe because the buyers recognize the breed they are crossed with (especially the WB
So in the end it really depends a lot on what you need to expect from the foal... If it's for yourself, if it's for sale, which disicipline you want to ride, the level of the rider who will be riding the foal.... All those things factor in.
This year we will have one purebred mare and one Clydesdale mare bred - I expect both to be fabulous... But they will be different for discipline suitability, I am sure.