Is it feasible to replace a C152's engine with multiple small turbine engines?
Have a look at the Cri-Cri propeller and jet versions.  Yes, jets can be mounted near the nose, but the plane must still balance at within its specified CG range.  This is why removing the engine in front and placing jets in back is out (unless you want to really go crazy and mount a Gatling in the front). Remember, it must balance.
However, at Cessna (152) speeds, props are vastly more efficient, so a $turboprop$ is not out of the question and, indeed, these are found on crop dusters.
&quot;Pocket jets&quot; are also found on motor gliders, and I have often thought of putting 4 of these on a sailplane.
However, another key consideration is how much stress an airframe can take.  With jets come higher speeds.  These planes are built to flying within a certain speed &quot;envelope&quot; regardless of propulsion source.
The &quot;Screamin' Sasquatch&quot; may interest you.  Here a jet is mounted on a sturdy bi-plane, and yes, it works.