Indeed right, except that I didn't consider that when the bottom BC547 is off and the top one is on, the capacitor would quickly charge through the base-collector junction! Indeed not what I want.
I instead put back the 557 with a resistor on the collector to limit the current (even though I am not sure it is necessary. I am opening another thread on this. )
---------- Post added at 02:31 ---------- Previous post was at 02:03 ----------
this solution, **broken link removed**, should do what I want and at the same time guarantee that the power dissipation in the transistor never exceed 500mW and that the current never goes beyond 100mA. Actually it should be somewhere around 75mA when the capacitor is fully charged. At the same time, discharge should be fast enough for my purposes.
WDYT?