I would go for option 2 or 3 or both.
You could redo entirely an divisional history (actions, accounts, battles, postscript) and then another book just like a photobook (Estonian Legion in Pictures, Latvian Legion in Pictures) with uniforms, equipments, miscellaneous for those who were interested in militaria, re-enactment but not too interested in academic research.
For the divisional history, I would like to read accounts on Ukranian veterans who parachuted back to Ukraine after the end of the war to fight against Soviets under the assistance of MI6/OSS/Germans, Ukrainian UPA-SB and SS Jagdverband cooperation in the fight against the Soviets, veterans organization etc. Maybe you have better idea, but it would be awesome to see the genesis of Ukrainian volunteers in the Wehrmacht/SS from Bataillon Nachtigall/Roland to the Ukrainian SS division and UPA. May I recommend that Professor Jeffery Burds would be the expert to look for in dealing about UPA after the war.
I know it's a huge undertaking but perhaps another chapter should be devoted to Ukrainian volunteers in Luftwaffe, Kriegsmarine, OT, NSKK, Schuma etc.
For the photobook, I would love to see materials such as, recruitment posters for the ukrainian SS division, SS kragenspiegln design (Ukrainian lion and the Trident of Vladimir), Stalhelm with Ukranian flag decals, Ukrainian SS belt buckles, weapons, uniforms, vehicles,.
However I am slightly worried that writting a book with such a detail about the Ukrainian SS might backfired since your book might be used by certain groups with intent to witch-hunt down surviving veterans of this division on possible charges of war-crimes regardless if they had been cleared by the governments of US, UK or Canada etc.