So I’ve spent the bulk of my EVE time in wormholes. Not too much nomadic, but I have done it with an Orca (and sometimes by accident when getting my orca stuck on the wrong side of a collapsed WH, but that is a different tale).
So first off, I wouldn’t necessarily agree with your initial premise. The orca’s SMA is pretty big at 400,000m3. You can easily fit 4 cruisers and a frigate inside, which should be more than enough for most wormhole activities.
Strategic cruisers on top of that are well suited for WH life. Heck with the last round of changes they are even easier, to the point you can be nomadic in WH space solo with just some fittings and a depot.
Even if you wanted more SMA space, I’m not a fan of trying to change the bowhead. It is a capital sized ship like the rest, so trying to make it smaller IMO isn’t a great option.
Personally I think a cooler solution would be to have adjustments available via modules (or rigs) for the orca. You could have some that give you increases to SMA size, maybe at the expense of other cargo. Or you could make the bays modular. So for example you have basically 3 cargo bays. Cargo, ore and SMA.
Maybe you are just using your orca to haul, So you put 3 cargo bays in those slots for max cargo. Maybe you are hauling ships, so 3 SMA. Or maybe for a fleet mining op you dont need cargo or ship storage so you go 3 ore hold for max ore carrying.
That would actually give the orca lots of flexibility, not just for this one case but for all orca users.