A greater indemnity, especially spaced out over a greater number of years would make the Third Republic even more unstable than it was IOTL. The Third Republic owed the Kaiser 5 billion francs after the war, which were paid off after only about two years, sooner than expected. If the sum had been closer to 5 or 7 billion francs, spread over a decade or more, you would have had German troops occupying parts of France for a significant amount of time.
The longer the average Frenchman on the street has to come in contact with German soldiers on a daily basis, and the more he associates his government that he pays taxes to as tributary to that power, the greater the resentment he will feel towards his foreign foe, but just as importantly, his own government. The Third Republic was seen by many as a temporary creation, and its legitimacy would probably have been severely undermined if it was forced to allow German troops on French soil, and pay the Germans for the long term.
A collapse of the Third Republic becomes more likely in my mind if the Germans press them hard enough. What follows is hard to tell. Anything from an Orleanist restoration to a radical workers republic is in the cards. What is unchanged is the regime's hostility towards Germany. Of course a radical or reactionary French state may have a hard time forming alliances against Germany like the Entente Cordial, and especially since could always find themselves humiliated in a colonial war against Japan, or even Great Britain.