Well, don't you think that a strong, centralized, independent Marathans would not be involved in the colonial race? This map is from ATL 1900.
clendor
If a Maratha state properly organised itself so it became co-herent and stable it could well rule most of India. If it did it early enough to quickly replace the Maghuls it would probably be able to stop or at least keep to the margins the European rivarlies and conflict that occurred OTL.
However it would still have serious problems:
a) Internal Muslim rulers, the Sikhs and probably some other elements would seek to maintain their independence.
b) the caste system which greatly impedes social flexibility and hence economic development. Along with the highly fragmentary nature of India which was more of a collection of vaguely related groups than an actual nation.
c) To develop into a modern technological state needs more than imported weapons or even importing the factories to build those weapons. This is vastly more difficult as it requires major social changes. You not only need to act like a European but also think like them. Several fairly powerful groups sought to do this in OTL but many failed [Egypt, China, Burma, Vietnam, to a lesser degree the Ottoman empire and Persia]. Those are the more well known but there were a lot of others. Only Japan really became a 'proper' industrial state before the modern age, and arguably India under the Raj.
As such I can see a Maratha state becoming dominant and probably holding most of India together. However without overcoming the problems mention above they are unlikely to become a modern industrial state by say about 1900. In that case they will stay play 2nd fiddle to the European powers and if they start trying to expand outside their basic sphere they are likely to come a cropper.
Afghanistan, unless you're planning on the ethic cleansing route is virtually impossible to control in any meaningful way, as various super-powers have shown.

Thailand and Burma where reasonably powerful and co-herent states and are likely, if threatened by a large and meanacing India, to look to a more distant protector. So even if they done't defeat any Indian pressure they can probably look to offer trade concessions to a European state who will do the job. The states in the Malayan peninsula have the extra factor of being Muslim, who wouldn't look on an Hindu conqueror very friendlily.
As such, while I could see a Maratha India under very good [and lucky] leadership, staying co-herent and largely independent it would have a huge task modernising the state in a way to compete with the other industrial powers and that would probably preclude it taking part in any colonisation of neighbouring regions because just about everywhere would be snapped up before it become powerful enough to do so.
I think you would need an earlier and possibly more dramatic POD to enable an Indian state to become a major colonial power in this time period.
Steve