It is most unlikely that there is any way to force Revenue to reduce the penalties and interest. In fact Revenue often hold off on the full amount they could charge to use as a lever. For example treating undeclared income as gross when they could in fact treat it as net.
There may be scope for talking through the matter with the Revenue Inspector, they usually like a quiet life. Understand how the penalties were calculated, was a penalty applied to the declared VAT matter. Are they calculating Interest from the year end or mid year.
However penalties and interest at less than 50% of the actual tax due is not huge given the time scales involved. Penalties and interest can easily amount to the same again as the tax due. It may be that they are already being quite lenient with you.