It is unwise to have same VLS for SAM and ASCM.
It's not unwise - that's the way both USN and PLAN work. That's a very smart way to accommodate ship's missile systems. The reason why IN can't do the same is not because we wouldn't want to but because we can't!
For India this can't work because our SAM cells are designed for accommodation of Israeli-origin missiles and our strike-length UVLM cells are designed to accommodate Russian-origin anti-ship/land-attack missiles.
Russians & Israelis have no obligation to design their missiles in such a way that they fit into the VLS cells designed by the other party. But US and China use locally-designed missile systems, hence they are able to make missiles that fit into a larger infrastructural domain that underlines commonality and near-infinite flexibility & adaptability.
Indian SAM is light-weight and sleek. It needs very little space. Brahmos on the other hand is heavy and bulky. It is better to have separate SAM and ASCM launchers to save space.
How universal VLS like Mk.41 works is that a cell capable of storing 1 big missile can accommodate 2 or upto 4 smaller missiles. This is quad-packing. If dealing with a small SRSAM like Sea Sparrow ESSM, you can put 4 missiles in a single VLS cell.
And again, the reason why we have separate cells is not because we wanted it that way, but because we couldn't have it any other way.
Regarding ASCM, the whole point of having a destroyer is to destroy enemy ships.
No, the point of your destroyer is determined by your naval doctrine. If your destroyer's focus is AAW (protecting Carrier Battle Group from enemy air & missile attacks) you may not be bothered even if your destroyer has very limited (or none at all) long range anti-ship capability.
The Royal Navy's Type-45 DDG is an example. I think most of them don't even carry a single ASCM and even when they do, they are designed to accommodate only 8 Harpoons.
If the number of ASCM is limited to 16, it defeats the purpose of destroyer.
Nonsense. For a ship without universal VLS, 16 is very very good number.
Daring-class (UK)
Horizon-class (France)
Orizzonte-class (Italy)
Baden Wurttemburg-class (Germany)
Type-052C (China)
Alvaro De Bazan-class (Spain)
Fridtjof Nansen-class (Norway)
^^ All those have only 8 ASCMs. In surface warfare, the Kolk beats them all hands down, just with what it has now. Remember China only afforded the ability to have larger number of ASCMs only once they installed UVLS on their Type-052D. Before that, 8 ASCMs was standard fit for any PLAN main surface combatant including DDGs and FFGs.
In comparison IN had 16 ASCM package on DDGs designed in 90s like Delhi-class. Heck, we put 16 ASCMs on a farking Corvette (Kora-class)!
So, more ASCM are needed.
IN already has more than enough love of ASCMs. What we need now are more SAMs.
However, not all of them needs to be Brahmos.
Across the Navy? Sure. We will have both BrahMos and at least 1 other type of smaller ASCM which might or might not be subsonic for the smaller ships.
But more than 1 type of ASCM on a single ship? That's probably not gonna happen - here or in any other country*
* Not including SAMs or otherwise re-purposed missiles used to attack ships.
Nirbhay cruise missile is also a good enough missile for most of the smaller ships and gun boats.
1200km LACMs on gun boats and corvettes?