Yes, you should be able to use whatever hardware you want. OPOS is supported for the peripherals. You'll want to think about how your local and remote printers are currently setup as you'll have to use direct serial (or OPOS) instead of IDN.
Also, you may want to look at the WS4s from your dealer since they may not be that much more than a generic solution once you factor in your labor and the what-if scenarios (Is it a bad mag reader, or am I just configuring it incorrectly...)
And a refurb Eclipse should be somewhere south of $1000 which may appeal. You've already got some Eclipses and they're probably not all completely junked, so you have some value in those parts and casework.