Can you can do magic? If so, for the extended version, how about adding any/all of: Great - (quiet) 16'; Choir - 2' flute, and (to be drawn with a soft 8' flute to make a sound for soloing) a nazard and/or sesquialtera?
Thanks for those thoughts ... the specification of the extended version is still rather up in the air. As well as the Tuba and 32' reed and flue, I had planned to use the Swell Geigen Principal 4' to provide a 2' Fifteenth on the Choir - I've tried this with the Choir flutes and diapason and it sounds good. The Choir Viol di Gamba is a very nice stop and it would make sense to try a viol celeste by repitching that rank.
To answer your suggestions - there is already a 2' flute on the Swell which works well in combination with the Swell Stopped Diapason. The Choir could be used to accompany that combination.
A soft 16' on the Great ... well, the Swell Bourdon is probably a good candidate. Would it be sufficient to have that available to couple, or would you need to have it separately available on the Great ?
Regarding the Sesquialtera - probably the most difficult of the lot ! Possible, yes (and probably best placed on the Swell), but I wonder how it would sit on this sort of instrument ? Considering that brings me to the biggest question - when planning an extended version of an existing instrument, how much respect should be paid to the style of the original organ ?
For example, if you were to go back about 30 or 40 years, you could easily find organs from this sort of period being rebuilt with neo-baroque positive divisions, to say nothing of the revoicing of the existing pipework .. all following the fashion of the day.
Of course, today we are far more conservative (for the most part !) and tend to value what we have and any additions tend to be more in keeping with the original pipework.
Should the same rules apply when doing the same with a virtual organ - or is it a case of anything goes ? I really don't know the answer to that - all thoughts welcome !
David