Hey guys, I'm looking for some advice on a tough basement question.

Here's the background: Our house was built in 1928 and believe it or
not, the concrete floor is in great shape. There are no cracks
whatsoever, and it is 99.9% of the time dry. The basement is split in
half, one half is the workroom and the other half is a finished part
that used to have wall to wall carpet with an underpad.

Well, living in NH, we experienced a couple week's worth of constant
rain in May that caused a ton of flooding statewide in parts of the
state that are not prone to flooding. In our case, I'm sure the
problem was that the water table rose too quickly and submerged the
basement. The water seemed to seep up from the floor, not come in
through walls or anything. It only ever accumulated to about 1/4"
though, nothing too crazy.

Anyway, our carpet was ruined and now we need to figure out how we
want to resurface the finished part of the basement. The trouble with
the concrete is that it is painted in spots and very very rough
(although no cracks). Also, it has a few (very few) spots that bulge
upwards (less than 1/2" though).

We've decided that we want to lay FLOR carpet tiles
(http://www.interfaceflor.com) in the basement. They can be laid on
wood, sealed concrete, tiles, etc.... Now the concrete itself is too
rough to accept these tiles so we're going to need something put on
top of the concrete.

I was first thinking of laying Ditra down using thinset, but now I'm
shying away from the idea... .first, it is a horribly tedious job
trying to clean up the paint which I'm assuming needs to be removed
for the thinset to adhere properly. Also, I'm not sure if you'd be
able to "feel" the Ditra underneath the carpet tiles since Ditra has
those square "bubbles"...

Our latest eureka idea was to just lay down pressure treated plywood
directly to the concrete and attach the carpet tile to the plywood. I
know it would be better to have 2x4 spacers fastened to the concrete
and the plywood attached to the spacers, but this is not an option as
our current headspace is hovering around 6.25'.

Do you guys think it would be ok just laying down the plywood directly
to the concrete, shimming where necessary? Or should I use 1x3 furring
strips instead of the 2x4s just so I have SOMETHING (I have a feeling
they won't be solid enough, though), or should I definitely go with
the Ditra and not worry about the thinset on painted concrete since
the paint is old and doesn't seem to be sealing anything anyway?

I assume the plywood would have to be fastened using a powder gun, right?

And finally what about this crazy idea.... just spread out some sort
of skim coat of cement to even out the concrete, seal it and apply the
carpet pads directly?

Again, this basement seems to only get water in record rainfall
incidents, and even then less than 1/2" of water... would it be ok for
the plywood to just sop that up since it's pressure treated, and we
can temporarily remove the carpet tile in the affected area to let the
plywood dry out.

Any advice is welcome,.. .thanks guys.

G