If you want the hybrid and animal forms to be mechanically different, you could buy Beast Change twice. Or you could use this:
QUASI-MODULAR ABILITIES [-Varies]
Description: You have the ability to alternate between multiple powersets.
Musts: You must "pre-pay" a number of refresh points equal to the total value of each set of powers that this power affects, plus a surcharge of one refresh.
Skills Affected: Varies.
Effects:
Two Powersets. Pick out two sets of powers, each with a total refresh cost one less than the cost of this power. You may use either set of powers, although it takes a full action to go from using one to using the other. The GM decides what is and what isn't a valid choice for inclusion in the powersets provided by this power.
Item Of Power Collection [-0] You own multiple items of power. Design a number of Items Of Power equal to your Resources skill. At any given time, you may use or loan out items with a total refresh cost up to one less than the refresh cost of this power. You do not receive the Item Of Power discount. If you have the Tracing power, then you may summon and dismiss these Items Of Power out of and into thin air. If not, you must treat them as physical objects.
I honestly don't know about the upgrade-ability of powers.