In addition i see you are looking along the lines of the bush box. It was their over engineering that has put me off, plus the XL is not quite big enough. It would be great to see size options on this stove you are making. We all have different wants i guess.
Going off common pot sizes:
'XL' - 4x medium 15cm-ish pots for the larger family. - Say a 35 cm square opening for a little space between pots.
'Standard' - 4 small 10cm-ish pots for a couple, small family, hiking group. - Say a 25cm square opening for a little space between pots.
'Mini' - 2 small alpkit/evernew style pots [like the mytipot1350, mytipot900 or mytimugs, very common styles and sizes] - Say 25x12.5 or 31x15.5cm, probably the latter is more universal since it will take most small pot/frying pan combo's.
They would also take nests well, for example:
Using the sizes given the 'standard' would have a cross section of just over 35cm corner to corner, allowing 15cm pots in opposing corners with 10cm pots in the other opposing corners (with a little wiggle room); that has common small nests covered. The 'standard' would get my money in a heart beat for a group stove [2+].
The 'XL' would have a cross section of just over 49 cm corner to corner, allowing for two 24 cm pots in opposing corners and 11cm pots in the other opposing corners (with a little wiggle room). 24 cm is rather big, so drop that down to 20cm if desired for the larger pans and increase to 15cm for the smaller pans if desired; that has larger nests covered. I personally wouldn't carry something this big aside from campsite camping, but others would.
Nests of approx 10-15cm and 15-20cm seem quite common. These formats could actually take slightly larger pot sizes (say an extra cm +/-) in a 4 pot config since the nest will decrease in size. Rectangular versions for larger stoves i think will restrict flexibility with pots (no massive stew pot for instance). A square would likely also pack more uniformly if one piece sides are used, and relatively speaking should have a better 'pack size:usable space ratio' in comparison which will matter more for larger stoves.
The 'mini' comes into it's own by being compact enough for 1-2 people yet not overlaping with the honey/hive in size. I think a 2:1 ratio would be best with two alpkit or evernew style pots in mind (two pots or burgers, leaving the trangia free for a brew). There area good number of pot/pan combo's <= 15.5cm, so unless the weight is vastly different i would use the larger of the two 'mini' diameters. It might seem daft to cater to these designs of pots, but alpkit mimick popular models, evernew are a huge brand. Both brands are expensive to replace, whereas ss billy cans can be picked up cheaply to suit and many come in to those measures anyway. The larger stated dimensions for the 'mini' make more sense unless you are a true gram weenie, especially since you won't have the same options for a larger pot as you would on the 'standard' or 'xl' square designs. i would also buy one of these in titanium for two person use, especially if it catered for <=15.5cm pots.
The standard and mini are arguably a weight saver for UL hiking too if done right on a titanium model. Assuming 3-4 of you use it and would otherwise be carrying a hive/honey stove each to save fuel on an extended trip it probably works out lighter if one person took a large, light box stove and offset their weight by putting some food in friends bags (we have done this before for shared tents etc).. Groups of 3-4 using a 10-12 cm pot each, again, are common. So that is another selling point for the 'standard' and 'mini' dimensions.
Trangia integration seems a low priority on multi pot stoves since you would need multiple trangias. If you have a trangia you probably have a small pot stand [perhaps the pocket stove] too. Basically i wouldn't sacrafice functionality of any form to accomadate a trangia, if it is easy and won't impede the wood burner in any way though sure.
If only one was going to be made the 'standard' would cover the common nests, cook 4 decent sized burgers and fit in most backpacks (assuming each side is one piece); whereas the 'mini' is far more practical for my common trips [1-2 people]. If i factor in my meths burner in combination with the 'mini' it would provide space for two 10-12 cm 900ml pots or two big burgers while the trangia handles caffeine.
It would be a very hard call if only one where to be made from these sizes i would want the 'mini' and hope for a standard to come out down the line (if it didn't i guess i would buy 2 mini's!).
You then have the hive, honey and pocket for single pot systems of varying sizes ofc. I guess you could add an optional base plate and flame diffuser (just a second bottom panel perhaps?) to newer models to stop ground burn and cook a burger or a few sausages on high flame. That is a very comprehensive range of stoves covering all bases aside woodgas.
Hope this helps in some way.
EDIT: You mentioned testing, mr obsessive here has spare time to test ..
