Came up with two theories for the multi morphing.
#1: I think Ax calls it an actual technique while "making" his human morph. We know that DNA is stored in "bubbles" within the blood stream, but it was never specified if it was specific individual's DNA in each bubble, or a general species bubble. If it is specific individuals in each bubble, then the technique probably involves aquiring only a little bit of DNA at a time, in a short time interval, making one complete DNA sequence.
However this suggests that the DNA sequence is just for the individual morph, and the morpher cannot choose to morph any individual that they aquired without re-aquiring. This theory is supported by Ax re-aquiring Jake when Jake was infested. I'm not too sure on this, but I'm pretty sure Ax aquired Jake then Yeerk-Jake freaked out, cementing the fact he's infested.
But with Elfangor, he aquired his human morph over several drawn out periods of time. This supports my other theory, that within these species bubbles, lies sub-species bubbles. ie., if you aquire Jake, Marco, Rachel and Melissa, their DNA will be stored inside the Human bubble, and 4 separate bubbles for each individual. The morpher can choose to morph elements of all 4, or an individual. The DNA information is drawn from either the whole Human bubble, or one of the four sub-bubbles.
The example with Ax above disproves theory number 2, but at the same time, the example with Elfangor disproves theory number 1.
That leaves theory number 3:
If you aquire only a little DNA, it's an incomplete sequence. You cannot morph an incomplete DNA sequence, and it remains incomplete until you add more information. So, Ax aquires a little bit of Jake, Cassie, Rachel and Marco within a short space of time, making a complete DNA sequence, allowing him to immediately morph into his new human form.
Elfangor encountered his "doners" over a period of time, until his sequence was complete.
I could've posted only theory 3, but I worked it out as I wrote this, so I think you should see how I got here.
If this theory makes any sort of sense to anyone else, then it must follow that the amount of contact time between the donor and aquirer matters, which is probably why the sedation was built into the technology.
Who came up with the two hour time limit? Why two hours? If it wasn't designed, how did they discover that two hours is the limit? If it was designed, why include a limit at all?