Hey and welcome to Seibertron!
Ahhh an MP collector. One after my own heart
I think this needs to be tackled on a case by case basis. It appears with the announcement of MP+ Sideswipe, that the MP+ will be continuing, and not just a one-off. But I'm not sure every figure previously released (after their decision towards hardcore cartoon accuracy) will be a candidate. Just from the figures you mentioned, Thundercracker (Asia's MP11T) already has a toon accurate scheme. As does MP17 Prowl. But then there's MP20 Wheeljack, who sorely needs the MP+ treatment.
I feel that patience will be your best friend in this endeavor. And here's a couple thoughts:
1- I highly suggest you keep an eye on whatever local resources are at your disposal for second hand figures. For me here in Canada, I'm a member of a local TF Fan Facebook group which have netted me some amazing deals. And then there's Kijiji, which is like Craigslist but not so scary. Do you have an equivalent in the UK?
2- There's no telling what Hasbro will release next. Unfortunately they seem to only be good for 1 or 2 MP figures a year, but it is still a resource.
3- Takara inexplicably reissues stuff all the time. The most recent ones that come to mind are Soundwave, his cassettes, and Starscream. All were earlier this year I believe? It also seems common for a figure to be reissued closely after its initial release, one of which did this I know for sure was Ironhide.
4- Watch online stores. If you're looking for brand new ones to preorder, keep an eye on places like
HLJ. If you're looking for older ones and at a decent price, there's second hand stores like
Mandarake. Both have worked wonderfully for me.
5- Avoid eBay. I actually rely heavily on eBay, but if I'm looking for MP's I stear clear. It is flooded with KO's and I would not be confident at all MP shopping there.
If you want, you can drop me a list of the specific MP's you need and I could advise you further. Hope this helps