Putting business processes into code ever again is a sure recipe for a failure
I would say implementating an ERP system the "normal way", with business processes defined in the code alongside many low level and unrelated functions are just sure way to get into another trouble. Only this time, as things have sped up in the business in general, this trouble is going to surface sooner rather than later.
So what to do?
I would suggest taking only financial modules from the original package as bookeeping and other finance functions do not eveolve fast. The rest, and especially all market-related processes (as CRM and even production and other processes that are definitive for the chosen business model) are ever changing so process engines seem the only good bet in the long term. How processes defined in those engines are presented to users is another question (some kind of portal, probably). The real issue is this: making process definitions modifiable on a daily basis and without the need to ask a vendor to do it.