I am walking this path for a while now - an IQEX… in process of building a new one, based on what i’ve learned in past 2 years with it.
To start I used cheap i3 style IDEX (Tenlog D3 was my choice), threw out crappy boards and did height adjustable toolmounts (very important). Used Duet2 + Duex5. Then just doubled the IDEX axis and viola, got IQEX… at this point, i use one as IDEX and one as IQEX. Daily.
So this is totally doable and huge advantage when you want high output.
What you want is take time and assemble the thing VERY precisely. Everything square and BOTH X rails EXACTLY parallel and square to Y and Z. Not a huge challenge, but I for example didn’t think of this when building first time.. fixed that, learned something. Making a jig on which you assemble the X gantry so that both X linear rails sit flat and then you torque everything up helps a bunch.
Whoever relies on meshbed levelling is doing stuff wrong. Yeah it’s nice, but you tram the machine and level the damn flat bed. Then you print on it with absolutely no problems day in and day out.
Disadvantage: with i3 style, Y axis is only one so while you can do multiplication, you can only mirror in X direction. Not huge disadvantage & still has better output at the end of the day than any “i printed a benchy in 10 minutes” gimmick. Machine is not realistically encloseable tho.
Works absolutely fantastic for about 1000 bucks printer.
What i am doing now is a box design - so XY plane is moving and bed is on the Z. It uses (well it will eventually) 2 stacked double markforged kinematics. Something similar to Muldex printer, but doubled.
Is it worth it? Not really sure. Should be fast as hell compared to my current i3 IQEX. More silent for sure. Encloseable. Insane output. Etc. Still, if concept works, then i will have to scale the design up to like at least 600x600 mm buildplate so this monsters electronics and build price are justified.
If this triggers your heart, i do posts from time to time on my FB group (“Marx group”. As in Marks’ group, not in marxistic way )