If I solve 67 I'll try Mara, but the more I look into the topic I believe less in MARA. The question is it the only solution? Or is it hopeless against the BOTs, if so then you shouldn't waste your time/money on 67. But I'm not an expert
I already told you guys the other and only valid solucion is mine your own block or get contact with a miner (an expert one) and reach some agreement to include your TX without reveal it on public mempool.
this may be difficult because most miners stick to already proven methods and they aren to modify their process only for one extra transaction.