Well always remember that a battle barge / strike cruiser is what it
does not what it
is. With that in mind you have huge freedom to proxy, kit bash, and repurpose anything you want pretty much. The current Compendium, for instance , has a dauntless retooled for marines in one of the pictures. Another thing you can do is cut down the size of a traitor cruiser to make it a light cruiser chassis by removing the first weapon bay section and pining the prow back on. This would be rather apropos for a 1st or 2nd founding chapter fleet which could in all likelihood have old vessels like this still.
Here's a WIP of a schismatic class lt cruiser I have on the work bench
