I sort of agree with this, although not all of it. I still believe that returning the cape colony to the Netherlands was still possible during the congress of Vienna (after it it isn't). The British had already returned it to the Netherlands in (I believe) 1805. The problem is that Britain kept the cape colony, Ceylon and western Guyana, because the Netherlands gained the southern Netherlands. An even stronger Netherlands (although Luxembourg as part of the Netherlands instead od a personal union isn't realy a stronger Netherlands), would mean that the British would keep more colonies (my guess would be the Dutch colonies in India or the rest of Guyana/Surinam). I could see the Dutch keep the cape colony if they don't get (all of) the Souther Netherlands, with some deal with the British, that the British are alowed to use the cape colony when going to India and the eastern part of south Africa becoming a British colony.
Ceylon is very unlikely to be returned.
I still consider it possible for the Netherlands to gain Malaysia. They still owned Malacca and the British had two other colonies there, Singapore and (i think) Penang. Singapore could even be butterflied away with a POD in 1815 (although I am uncertain about the likelyhood of that). Malaysia always was in the Dutch sphere of influence, so I can see a different deal with the British in 1824 in which the Dutch gain Bencoolen and Penang, while the British gain the Dutch Indian Colonies. Of course the Netherlands probably needs to offer something else as well, maybe the Gold coast colonies, maybe Surinam (or if they still have it Ceylon).
A Dutch colony in Ghana is as I said certainly possible. OTL many Dutch didn't agree with the sale to Britain. This will probably not lead to an entire Dutch Ghana as there are still some British colonies there. I can see a stronger Netherlands (one that still includes Belgium) keeping the Dutch goldcoast and even buying the Danish trading posts. To create a decent colony out of it the Dutch probably need (some of) the English trading posts. I suspect that if the Netherlands keeps their trading posts some deal with Britain is made in which various trading posts are exchanged forming two continuous sets of trading posts after wich two colonies are formed in what is now Ghana.
Dutch influence in China is possible, just like there was French, German and British China. It basicly depends on the history of China after the POD and how influential and interested the Netherlands is at the moment the Europeans decide to do something in China (assuming this isn't butterflied away). A united Netherlands will be more influential, so it is more likely. If they might be interested, i am not sure about that (actually I think they won't be).
Dutch Philipines? I doubt it; you need to go to war with Spain over it and I really don't think the Netherlands will do that.
In short: For the Netherlands to regain their colonies after the Napoleontic wars and gain the Southern Netherlands you need a POD somewhere during the Napoleontic wars (or even before that). Maybe you can get a Netherlands which has western (British) Guyana and Flanders, but I suspect to gain the Cape you have to give that Flanders up to.
Other colonial gains for the Netherlands are part of the Goldcoast after a deal with Britain, Northern Borneo, western New Guinea and nearby Pacific islands. Malaysia isn't out of the question, but only if the Dutch give up other colonies. Singapore if founded will probably remain British. The Netherlands will most likely not be interested in the Congo.
I believe that with a POD prior to the Conference of Vienna, the Netherlands can come out of it with at least part of south Africa as their colony. For instance, I agree that the British would want to keep Natalia or the eastern cape as their colony, but I think the Dutch could strike some deal for the rest. Perhaps if there was a POD of the British losing the Battle of Blaauwberg, then Cap Colony would go in full to the Netherlands. However, I don't think a British loss their would seriously affect the outcome of the Napoleonic wars.