Feature request: use higher fee as default

[Grinder]

I would appreciate if it was possible to increase the default fee, for instance by adding a configurable multiplier (ie 1.5 to make all levels 50% higher) or by allowing to set the highest level as the default. I forget modifying it when I send, and last time I used it the transaction was only accepted after 110 minutes and in the 8th block that was found after I sent the transaction.