I would not recommend trying to encapsulate failing paint. The areas that aren't peeling yet probably aren't far behind. I would definitely look into the cost of just replacing the trim. You'll still need to take precautions to prevent environmental contamination when removing the trim instead of stripping, but it will be much less of a headache. Remember that the hazards of lead paint removal go far beyond your own personal safety during the removal. You do not want this stuff in your yard. It's not something that just goes away after a few rainstorms. It stays there and can potentially make the yard unsafe for gardening or recreation.