If you do decide to fly DL and want to obtain lounge access quickly, I see that SkyTeam member ITA Airways is -- for one more week only -- offering a free status match to members of certain other FFPs (including BAEC). Details here:

https://onemileatatime.com/deals/ita...-status-match/

("Lucrative ITA Airways Volare Elite Status Match Offer")

I think that Flying Blue is currently offering a paid status match to mid-tier elite status for €199. I do not know enough about the ITA FFP or Flying Blue to say if one is better than the other.