I see potential for a third option. The Behringer FCB1010 can be set up to merge MIDI In data with the pedalboard-generated MIDI messages, and send them both to MIDI Out. See the 2.2.3 Global Configuration page for details.
Space [XMT] -> FCB1010 [MIDI Merge enabled] -> ModFactor [THRU] -> back to Space MIDI In
Space could still generate MIDI Clock, passed through the FCB1010, and on to ModFactor. The FCB1010 could generate Program Changes and MIDI CC messages for the ModFactor, and on to Space. Since Space is effectively "blocked" by the XMT setting, there shouldn't be an infinite MIDI loop (set up by the closed circle of MIDI connections).
That's the theory, anyway. It's something to try out before spending money on MIDI splitters / merge boxes. I have an FCB1010 here – set up in a somewhat similar fashion – but I use a master external MIDI Clock outside the pedalboard, with everything else set up to THRU.
