Thank you all for your replies

My problem is I'm trying to juggle a few conflicting requirements in doing this new vero layout.
On the one hand I want to minimise part count and simplify things, but making some of these improvements will increase the part count.
Stephen's link is interesting for 2 reasons. One is that all BBDs are given the same bias level. The only other example I've seen of that is in the BYOC Flanger.
Also, I think I read a post by Mark Hammer mentioning he'd used a single bias level for multiple BBDs and that you can often get away with that (presuming the BBDs have the same supply voltage). I'm therefore inclined to leave the bias scheme as it is because it saves me adding more components and coupling caps to the BBD inputs.
I'm aware that the
optimal bias level will vary from device to device. So Larry, when you say that changing a BBD can mean you need to re-bias, do you mean that you need to do that because the
optimal bias level has changed (i.e. it's not an audible difference, but you can see the difference when you go through the bias procedure with a scope), or do you need to rebias because the new BBD bias point is so far from the old that you get noticeable clipping if you don't rebias?
The reason I ask is that I'm not concerned (at the moment) about tweaking every BBD to its optimal bias voltage, because I've seen that there's actually a small range of bias voltages that let the BBD work OK without clipping the guitar signal. All I need is for there to be an overlap between the range of OK bias levels for the two BBDs. I've got around a dozen MN3207 to experiment with and I'm hoping that once I've set a single bias level, changing ICs will still keep things working OK with no clipping.
The other interesting thing from Stephen's link is that only the last BBD in the chain gets a trim pot to balance its clocking noise at the output. All the other ones just have the inputs tied together, (presumably because using resistors there is worse for S/N than using a current sink) ? I've also seen that many pedals don't bother with any sort of BBD output trimpot (Original EM, MXR 117, Morley Flanger, Foxrox Paradox TZF, Boss CE-2, Boss DC-2) while other ones do (Deluxe EM, A/DA Flanger, Flanger Hoax).
I can see how manufacturing differences and ageing affects can change the bias requirements of one IC versus another, but is there really a big difference between the two sets of buckets within the same IC? I am inclined to do the vero in such a way that gives the builder the option of using either fixed resistors or a trim pot at the BBD output.