I'm no building expert, but I don't think your foundations should be at risk if you fill the hole with topsoil - the water should just drain away, same as it does now.
What way does your front garden face? I think I would bet tempted to put in fragrant plants that smell lovely as you enter and leave. Sarococca confusa has an amazing winter scent, as does Daphne odora, though the latter won't appreciate deep shade.
If it's south-facing then ignore that recommendation for sarococca confusa - it's a shade lover. Daphne odora will love it though! Lavender is another possibility. Scented violets for ground cover underneath things might be lovely.
I wonder about something like a standard, small leaved lilac (Syringa pubescens subsp. microphylla 'Superba') which can be kept in a neat lollipop shape? Would look smart and could stand in the brick area between door and window and disguise that downpipe. They bloom for a short time, but the scent is like nothing else - it's gorgeous!