Fleetfoot Panther is part of a cycle of ally-color creatures that force you to return a creature of either one of their colors to their owner's hand. As such, I will keep the second ability on this panther. The first ability, however, demonstrates its panther-y-ness: the use of flash (The text you see on the card is flash but before it was keyworded to flash). And that's what we're going to change yet try to keep it feeling panther-y.
Panthers are quick, thus, the flash. I did a search of other Panthers in Magic: The Gathering, and they tend to end up being quick as well, with uses of the keywords haste and first strike. Haste is something that appears in green (but maybe not back then - meh) and white has first strike. I can use either one of these!
First, I must check out the other cards in Planeshift that also have this ability and make sure that they didn't already use haste or first strike.
So, I'll have to either use haste or something else!
Oof. Haste feels so wrong to include on a card in the past. Haste wasn't strongly established as something that green does back in Invasion. At least, I believe so.
Then I thought about reach and whether panthers can climb trees. ...Turns out they can! So, they need a tree to climb. Does this work, then?
"As long as you control a Forest, CARDNAME has reach."
"Tap an untapped Forest you control: CARDNAME gains reach until end of turn."
It could just have reach by default due to you probably having a Forest-like land from casting the panther in the first place.
Needing to have an untapped Forest to tap to give the panther reach does cause you to have the kind of gameplay where it feels like the panther is lurking in the trees. You keep that Forest untapped, threatening your opponent that the panther can gain reach to block a flier. So then they decide to perhaps back down because you had that forest untapped, occupied by a panther.
We could give the panther vigilance.
Looking over the rest of the uncommon cycle of these kinds of creatures, I notice that every single creature in the cycle EXCEPT the Panther one has an ability that triggers upon entering the battlefield. In this case, I can't help but to fulfill the cycle! But with what?
White and green effects:
Returning things from the graveyard
Destroying artifacts and enchantments
Flickering/"Oblivion Ring-ing"... wait. Interesting. Oh, wait, that can't be done due to choosing triggers in a certain way so that the creature exiled will never return. Well, poo.
Can't attack or block. (In this case, can't block. ...oh, wait, that's more a red thing.)
Then I stopped right here and decided on "Fruitdrop Panther" and how that relates to life. I'm thinking of how this panther knocks down some fruit from the trees or something as it leaps around, and you reap the benefits. This name fills the criteria of being named something that comes alphabetically between "Ertai, the Corrupted" and "Gerrard's Command."
...I also thought of Ferocity Panther, for giving +1/+1 to each of your creatures. Hmm. Maybe that makes more sense than a Panther dropping fruit. Yep, it does. Even though I am entertained by the idea of a fruit-dropping cat, I think associated ferociousness with a panther is the best way to go.
Then I decided upon a Giant Growth effect on a 3/3 body making more sense. It feels like the panther is helping out on the turn it came out (perhaps the advantage of ambush/surprise), which makes the effect make more sense on it.