I hadn't thought of Powell actually, my only thought is he could defiantly be PM later but is the 50's too soon?
Very much too soon. You've a number of problems with getting Powell to being a senior Army officer who becomes PM.
1. Powell was regarded by the army as being suitable for intelligence work and sifting through reports. He was considered unsuitable for combat operations. Powell himself viewed things differently, but for all his education and erudition, he wasn't actually that self-aware. The chances of him getting to a position where he could climb more rapidly than he did are slim (not Slim). About the only way might be to get him involved in the Boxes at Kohima, which is not out of the question. The trouble is, while that gets him into a position where he could prove his talent (or, more likely, stop a bullet from one side or the other) - assuming he had that talent which is an unknowable as he never saw combat OTL, it doesn't leave much time for subsequent promotions.
2. Politics. He first entered Parliament in 1950, and there's no real way to speed this up. Almost immediately, his inflexibility came forward, and he pissed off senior figures in the party by talking against measures they favoured. There's no real way of getting Powell to keep his mouth shut on matters he felt a need to talk about, there's no real way to stop his party putting forward the things he's going to oppose. There is going to be a period where the party leadership aren't going to touch him with a bargepole. It's only really in the aftermath of the Suez crisis, which ended a number of careers, that he started to make any moves forward, which means that his career effectively starts late 1956. OTL, he disagreed with the Government over monetary policy and resigned, consigning himself to brief obscurity. That was 1958, and it's only around here that we can realistically tweak things such that government monetary policy is in line with his. Smooth this out, and by around 1962, he's possibly sufficiently senior to be considered. However,
3. Personality. Getting to be PM involves making alliances and having people back you. I think it would be fair to say that Powell was not noted for his flexibility or his appeal to voters on a personal basis. For example, his attitude towards the Thalidomide victims was less than helpful (basically, he told them it was their own fault, so piss off; he used more elegant language than that, but they got the message). He's never going to bend. He's also going to totally piss off the Americans, which after Suez, would not be the best move. I can't see anyway he could manoeuvre himself to be PM. He was considered a risky choice as mid-ranking Minister; I can't see the party dedicated to being in power turning to him as leader.