I made something similar when I first started DIY carpentry, based on a design in a book called "The Complete Home Carpenter". I still use that bench after 30 years, so they must have got something right
I have 3 suggestions/observations :-
1) My bench tended to 'jump about a bit' and walk across the floor when doing something energetic on it. I didn't want to bolt it down, so I made the base hollow (about 4" deep) and filled it with builder's ballast. This both adds weight to hold it in place, and damps-down vibration. I was lucky in that I did this back in the days when we had summers, so I could spread the ballast out out-of-doors first to make sure it was really dry.
2) I'd put a shallow trough at the back of the top, about 1" deep by 4" wide - it's very useful to be able to put e.g. screws down on the bench, where they can't roll off or mark misplaced wood. Give the trough sloping ends so it can be brushed clean easily.
3) Not sure what you propose to make your bench-top from. Mine is 3 layers of chipboard, the top layer being screwed on from underneath. I've replaced my top layer 3 times over the 30 years since I made the bench, only takes a day and makes it almost like new. Chipboard is probably a bit harsh, you might consider a top layer of something kinder to the workpiece (beech kitchen top, perhaps ?).