I agree it would be very unlikely to live up to the original series, but it could work.
I believe the essence of Thomas Magnum is that he is – rather can be a very formidable and competent individual who has a knack for goofing off and not taking things very seriously (until after the second commercial break at the earliest). He is valuable and loyal as a friend, and attracts and inspires loyalty from all his friends, whom are by-the-way often frustrated by his sophomoric and irresponsible manner of proceeding. He is a good natured, fun, and gifted companion—but when he is absent it is easy to resent the fact that he owes you fuel money and yet zooms around in an (adjusted for inflation) eighty-thousand dollar sports car with a borrowed high end camera/telescope/laptop computer/etc. in the passenger seat. How does this near-do-well, half assed security consultant keep sleepwalking through life and ending up on top of the world. I mean, I mean I work hard and pay my bills and take care of my business- and this guy keeps falling into buckets of shit and coming out smelling like roses. Of course, when things get serious I’ve got his back, and there is no one I would want by my side more than Thomas Magnum when I face trouble.
Higgins CAN be a woman, and she doesn’t even need to be former military, she just needs a competency Magnum will subtly admire even as he makes fun of it. She does need to be a few additional things: 1) Persnickety!, 2) Entirely serious about everything- especially her duties on the estate, 3) A stickler for the rules (this is hinted at by the previous two points, but I mean a rule follower not just with Magnum, with herself and Robin Masters, certainly with Rick and T.C.) 4) she must resent Magnum’s easy manner and lack of maturity—but she MUST admire him on a very serious level. She must want him to live up to his potential more often so she can give him the deep respect he so seldom, but occasionally deserves. 5) She must not have-nor stir any romantic or sexual desires in Magnum (it would be a cute little sub-plot if she does have the hots for either Rick or T.C. whichever one she admires- the other should have the hots for her. A perfect- never executed triangle of desire). In her relationship with Magnum, she is the exasperated babysitter and he is the spoiled brat kid she must care for. 6) She must defer to Robin (who could also be female), but should often see him/her as a dupe falling for Magnum’s boyish charm.
That is an interesting possibility. Robin Masters doesn’t have to be an unseen Charlie (of Charlie’s Angels fame). I think that character should be an older female who can still view herself as viable in matters of love, but distinctively past prime; the way Joan Collins and Sophia Loren were in the nineties. She still needs to be rich and powerful, dropping in with a flurry of activity on her way to a writer’s symposium or the Milan fashion shows. She should be a re-occurring role played by an honest to god former heart throb that shows up about six times a season. One of those six appearances can focus on her for the whole episode if they get a good enough actress willing to work that hard once a year. The others can be a drop in where all her scenes shoot on one day. She needs to show the audience that she counts on Higgins everyday to run her estate. But that she lets Magnum sponge off of her as a way to keep him on retainer in case she really does need him. She has perfectly assessed the value of these two rivals and created a reality in which they each play to their strengths- and lets them suffer the consequences of their own conflict while she benefits from it.
Okay, too long. The paragraph below got me thinking and I went on and on and was nowhere close to a stopping point. Feel free to read it (it is even longer now I assure you), but it can be summarized thusly: The point is Magnum must carry a forty-five caliber Colt, he must have loyal friends and comrades in arms we see only once (or for a short arc), he gets all of his exercise from fun and exciting activities- he never has to go to the gym, and he should have a moustache
There are a couple of things concerning Magnum. First, the military now uses 9mm as their side arms. Somehow, Magnum must carry a 1911 .45 ACP. Perhaps a range instructor he befriended in his past has converted him away from the girlie NATO weapon, or his own personal taste, or it can be a gift from dying comrade in arms. His gun must look and especially sound different from the others on the show. Second, like Spenser for Hire from the time of the first run of the show, Magnum must a have long list of highly accomplished men at arms just out of arms reach; guys who can fight and shoot and owe (or are owed) debts of honor from fields of battle real and figurative. I mean beside the bunch of Navy Intel personal he cons into giving him info. This is a great way to get past prime action/adventure actors on set, and also up and comers. The guy who gave him his first job, the new guy he trained for a SOG raid. The guy who is feeling his age and wants to prove he still has it comes to Hawaii and gets the guys into all manner of conflict for no reason. The young guy cycling through Hawaii on his way out of the Navy with PTSD. The guy they all used to look up to who has lost his nerve. The guy who always saw all the angles but is now suffering with dementia (perhaps a former commander of Magnum’s or T.C.’s). A young guy who admires Magnum and heard all his stories and mistakes the exaggerated stories for a model and puts himself into terrible and unnecessary danger Magnum, Rick and T.C. have to rescue him from. (This would be an example of seeing one of those relationships I am suggesting exist at its beginning.) The point is there are others farther afield than Rick and T.C. who would drop what they are doing if Magnum asked them to, and would turn to him first if…… their wife is kidnapped, their kid runs away, they are blackmailed, etc. The thing that would make this a good gimmick, is that in each case they would remember and state some truism that sort of defines their loyalty to each other. Maybe occasionally they will learn that the secret that got them through overseas in 2003 is out of date and they need to improvise a new strategy- to remain flexible. There should also be a crossover with NCIS.