Instead of allowing you to take on a second form... what if it allowed you to cast it on an ally giving them a form you choose in there and in case you use "Animate Ally" they will be resurrected in that form. It could be used similarly with a textbox like revive or teleporting and I think it would be a fun option to turn your allies into zombies or liches if they are willing to.

The "you can only be in one form would still apply though". You can currently avoid this rule by being animate allied and already being in a shroud, but it should be fixed.

Deathly versatile rework: Deathly Community
Cast this ability on an ally to make them a zombie/wraith/vampire/lich and grant them the same bonuses you gain from this tree.

Animate ally rework:
The ability will have double range and can be used through walls. When targeting a soul stone it picks it up in your inventory, when targeting a player it revives them for 60 seconds in the form you have chosen as secondary.
Passive: When you die while having a soul stone in your inventory and is unaffected by a 60 second timer, all allies you held the stones of will reincarnate as specified undead for 60 seconds.
Cooldown reduced to: 30 seconds, but only once per same target. Reviving a player removes the ability of them respawning from soul stone.
Sp cost: increased to 60sp per cast.

The origin of idea:
Back then when I started ddo, I was looking forward to see animate ally, because i thought it would have a unique effect on allies, etc. It does have unique effects, but the usage of it is rare and sometimes not desired by people. So I thought having more control over these abilities would be a cool implementation even linking the 2 abilities. The reason I thought of this kind of change is because I think soul stones are only utilized as a means of where you can be as a ghost, but pale master could use it more creatively. Using it as temporary revive in the heat of battle is something a few people would look forward to, but if not at least this serves as an idea that soul stones could be utilized in some way. As for deathly verstaile, from my experience no one uses that ability and I think that being able to turn your allies into undead if they are willing to would be a good idea with interesting results.