Design advice when daisy-chaining multiple JTAG devices
1) Don't put very many devices on one bus.

2) If there's something for which jtag is really critical, and you need jtag extensions for firmware download or debug, put it on it's own separate bus so electrical issues on a longer one don't force you to run at a painfully slow clock rate.

3) See (instead or as well) if you can design end-to-end functional tests that would detect assembly or component errors, thus including coverage of the parts that don't have jtag capability.