While I consider the OBBBA largely a continuation of the TCJA (for individuals anyway), there is certainly a good amount of work that can be done to optimize older, middle-income taxpayers' liabilities for this year and beyond.  Between: (a) income planning (e.g., the timing of income, Roth conversions, social security, upcoming RMDs, etc.); (b) deduction planning (e.g., timing of SALT payments, PTET payments, charitable donations, QCDs, etc.); and (c) collateral damage (e.g., phase-outs, NIIT, AMT, IRMMA, etc.); it should not be too difficult to impress upon the clients the need for sound tax planning services.  While many of these tax items are 'optional' and multi-year in nature, and the possibility for new tax law before year end still exists, a solid tax planning package to address the inter-related / inter-dependent (and compressed) tax liability computation would go a long way.  ProSeries? Anyone? Bueller?

Rather than a shotgun approach as a new service to your entire client tax base, I'd suggest reviewing  select taxpayers and their specific circumstances since you're likely to find enough 'low-hanging-fruit' in a small group of clients for which your advice (and their participation/commitment) will likely pay significant dividends - to both of you, whether now or in the future.  One windfall (moderate or large) has a tendency to retain a client for many years.