Shame.
If he had become a Minister, what policies do you think we could've had France instigated regarding transport/colonialism etc?
I don't think that's much. Two words : Ministerial unstability. It was okay for social reforms, but outside Paris (that didn't had a mayor, it was directly ruled by the prefect) and the municipal powers that were more stable.
Of course, for having FdL minister after 1898, you'll need him to be more radical, in order to be part of a...well, Radical Party government.
I don't see how he could have done something, more than OTL really. The great works were mainly due or to universal expositions, or to municipal authority. Of course you had the multiplication of railway in France, but it would be HARD to make it even bigger.
Admittedly, he could have launched the Roudaire project of creating an inner sea in Tunisia...But it's likely to be abandoned because it was really unfeasible and would have needed awful lots of money for a probable poor result. FdL was really fond of this project OTL, though so it's maybe THE thing he could have supported.
Now, with the help op several batallions of butterflies, MAYBE that a french government could have supported that too. It's likely to turn like a Panama Scandal in OTL, though and end to make FdL looks like a crook at worst, and incompetent at best.