Should it be possible to use a T100MD2424+ in place of a T100MD888+ without concern? Judging from the specs on your site it appears the 2424+ is a superset of the 888+ with the only differences being the additional I/O, the use of terminals for analog I/O rather than D-sub (a good thing), and the addition of the MCR input.
Any hidden gotchas I should be aware of? Maybe differences in available PWM frequencies or stepper frequencies?