I don't think you can readily assume this. As of now, we know nothing of what became of Maul after Sidious defeated him on Mandalore. For all we know, Maul might now be a subject of one of Sidious' twisted dark side experiments, a la Darth Venamis... Although I could easily see Sidious trying to take advantage of the situation by leaving Prime Minister Almec a message (apparently from Maul) to rule Mandalore in his stead. So now Almec is a puppet ruler for Sidious instead of Maul, allowing Palpatine to keep a closer eye on the happenings of the Mandalorian-controlled neutral systems that I'm sure figure to be part of his plans further down the line, especially following the conclusion of the Clone Wars. You bring up good points, but given the four-part nature of the arc, there simply wasn't enough time for them to cover all their bases, so they had to hand Maul's faction the Idiot Ball for that episode. I mean, Obi-Wan and Bo-Katan's loyalists were able to infiltrate the prison complex easily enough anyway, so I'm thinking many of those supercommandoes might be relatively green recruits taken from New Mandalorian volunteers (of course, most would still be Death Watch). But you don't give Sidious enough credit. I'm sure he would have prepared for any possible contingency if he was so willing to personally go to Mandalore alone. I'll bet he had things under control on his way to the palace. Anyone he happens through that tries to get in his way would have been dealt with swiftly and mercilessly. I personally think the Shadow Conspiracy/Mauldalore arc could really have been improved with an additional episode (or two) to cover the takeover of Sundari, and the fallout from Maul's defeat of Pre Vizsla. The arc was a bit rushed.