What is the 'Remain' ability on your cards ET? Here are my thoughts on the idea.
Disciple, 6
|5
, 4|8, When Disciple enters or leaves play, remove all poison counters from a random poisoned creature you control. [Steal]
In/out is a nice idea, although 'in' can be isolated as can 'out' since often cards need not have both. Out triggers can provide a deterrent against destroying it, which is nice.
Reanimator, 5
, 5|4 [6|5], When Reanimator dies, a new Reanimator is summoned with 2 less Full ATK and HP. [Steal]
The first time it returns, it would be a 3|2 [4|3] maximum, and next time it would not return or be 2|1 if upgraded.
There are already quite a few 'in' abilities floating around, such as this one:
http://elementscommunity.org/forum/index.php/topic,4195.0.html