Here is how I manage this :

I write a different frontend/backend file for each frontend :

then when I start :

is doing : CPP−P−C−I HAPROXY_CONFDIR/HAPHOST−I HAPROXY_CONFDIR/backend -IHAPROXY C ONFDIR/frontend−o HAPROXY_CONF $HAPROXY_CPP

which basically rebuild one config file. Very fast and you still have
the flexibility to manually remove a frontend quickly.

Note that the genconf.py is old now and need to be fixed (header
manipulations…)