Most of that would fail horribly.
You can only blend DNA that is fundamentally the same, only DNA from members of the same species, you couldn't mix, say, a chimpanzee and a shark, their DNA doesn't match up closely enough, hell, humans and Chimp's don't.
And there ARE limt's to Z-Space, Morph something to SMALL, and you get sucked in and die, I don't know about BIG, but there is probably some kind of upper limit.
Also, HOW THE FUCK CAN YOU SAY A GIGANTIC NIGH UNSTOPPABLE DEATH MACHINE WITH LIMITED REALITY WARPING ABILITY ISN'T USEFUL!?
ACQUIRE RAMIEL (The movie version would be best, but either would work) AND YOU CAN RAPE STARSHIPS.
Angel's (Except Rei and, to a lesser extant, Kaworu) run ENTIRELY off of instinct, which Animorphs can access better then the species they morph into.
It's just a matter of riding those instinct's, directing them where you want them to go.
More importantly, they should be able to, once they get control, just shut the call to Adam off.
As an example:
When they became Leeran's, they could turn their psy OFF.
Leeran's CAN'T DO THAT, they CAN NOT DO THAT, they are INCAPABLE of turning their powers off, the Animorphs could, because they aren't Leeran's, just wearing the form's of Leeran's, they don't have to strictly obey the rules of the bodies they're in.
And, to finish: You can acquire someone or something through a fresh enough blood sample.
So all Shinji has to do is jam his hand into one of the huge lake's of blood the Angel's make when they die.