I'd like to see something modular. Like you can choose to make a 2/1 for 2 or a 1/3 for 2. Both reasonable bodies for the cost and they appeal to aggressive/control strategies respectively.
This sounds like a terrible idea to me. First, there is a very good reason why there's a uniform definition of what a face-down creature is. Having to remember / indicate which of the two modes you chose on each and every morph will get annoying fast. Second, the 1/3 option kills aggro. I mean, they'll have a burn spell or two, but when you can just block a Goblin Guide with a defensive two-drop every time because you happen to run a lot of morphs? Also, the 1/3 option straight up murders the 2/1 option. I don't like it.
In short, if you want to make morphs more playable, I would go for one clear definition of what a morph is. Be it a 1/1 for
or a 2/2 for
(don't do 2/2 for
, it's a dumb idea), as long as it's consistent.
In reality though, morph, by WotC's own admission, requires you to heavily redesign how your limited environment looks. When 2/2 for
is the baseline, you can't have creatures, especially at common, that beat that baseline 100% of the time. Why draft a morph, after all, when you can draft a 2/3 for three? That's going to beat every morph in the set! When you look at Khans of Tarkir, you'll notice that there are only seven cards at cmc 3 or below that can kill a morph and live, and only one of them is a common (
go on, have a guess!) and a further 3 are at uncommon. For reference, Battle for Zendikar also has only 8, but 3 at common and 4 at uncommon, and Kaladesh has a whopping 14 (not counting vehicles), 4 at common and 6 at uncommon. Note: I only looked at 2/3 or better stats, not at any other mechanics (like 2/X's with first strike) for this count.
Now look at your own cube and calculate the percentage of cmc 3 or below drops that can kill a morph and live. I'ld say chances are you are trying to add the mechanic to a hostile environment. I don't even know if 1/1 for
is going to fix that, since at least as a 2/2 it has a somewhat meaningful body. 1/1 is so anemic...
Perhaps the neater solution is to go ham on colorless support, with cards like
Vile Aggregate,
Tide Drifter and
Ruination Guide, but unfortunately, Wizards hasn't really gone out of its way to print a lot of those. Maybe a morph support package in blue-green? Or maybe ahadabans had halfway the right idea and 2/1 for
is an acceptable stat to cost ratio? Or both, of course