Just avoid the term "trickle charging". It is not well defined in context of li-ion, and will just trigger non-technical people who haven't got the slightest idea what they are talking about to start posting links to the well known fake information heaven, the Battery University.
"float charging" is slightly better but that causes emotional reactions in some people, too. So maybe just describe the idea as "CC-CV non-terminated charging".
While manufacturers of cells usually suggest terminating the charging, that will only result in microcycling between maybe 90% and 100% SoC (depending on charge restart hysteresis), which definitely is no good for cell life.
Most important in your "float" application, IMHO, is to make sure your CV regulator cannot (easily) fail as short circuit or otherwise output too high voltage. Keep it to 4.1V/cell, or even better, 4.0V/cell if you can afford that ~20% loss of usable capacity.
Assuming the cells are not seriously bad (increased self-discharge), even a non-balanced pack is an option. I know people here don't like it, but for example, Robert Bosch had no issues I know of supplying completely no-BMS power tool packs for years. I have dismantled a few after End-of-Life and they were in perfect balance. No cell-level monitoring, no connections to taps at all. But if you go that way, I'd recommend leaving more room for both charge voltage, and discharge cutoff voltage (e.g., 4.1V and 3.0V instead of 4.2V and 2.5V), and check the cell-level voltages with a multimeter manually every few months.