A language I've been sketching recently, Alhosör, is ergative-absolutive. 
Despite my lack of linguistic knowledge, I've managed to figure that out and
I think it's a much better way to treat noun phrases than nom-abs (but
that's another discussion).  My question is, is this system compatible with
active-stative contrasts in verbs?  I intended to use verbal morphology
(probably initial consonant mutation or ablaut) to change a verb meaning
"ride" (stative) into "mount" (active).

I like this idea because it gives me a lot of freedom to make implications
about the nature of certain verbs and the relationships of those verbs.  But
I fear that ergativity may render this distinction meaningless (and
therefore, diachronically, it would disappear).

Examples (where "ascend" is the unmarked, stative form and "lift" is the
a. John.ERG ascend = John ascends
b. John.ERG ascend.ACT = John climbs
c. John.ABS ascend = John was ascended
d. John.ABS ascend.ACT = John was lifted

Are c. and d. too similar?  Essentially, my question is, does an
ergative-absolutive alignment render an active-stative contrast unnecessary?

Note that I may be confusing active-stative contrasts with changes in
transitivity (valency?).  If anyone sees that my use of terminology is off,
please inform me.

Cullen Kain