If you're that desperate for a an RS1600i as your weekend Jolly save up and buy an ok one - 3k should see something half decent I think.

Defo not sell the S2000 to replace it with shonky old fords.

As for parts - in terms of old escorts - assuming the shell / panels is ok (which they wont be) and the interior is ok (which it wont be) the only thing you really need to watch out for is the metering unit on both and the ecu/coils/sensor lead on the 16i - but if it breaks you can stick it on a dizzy easy enough, the metering units prob get ok second hand - everything else should be within reason readily available - but Mk3's have a habit of munching things like Indicator Stalks - which prob aint so easy to get.

The tailgate will also be fooked btw.

Also... they dont have ABS aaaaand the brakes on a 16i are wowful even by early 80's standards.

And.. if you drive a Mk3 escort as a daily car - so 12k a year... even a good one will last 18mths tops.