Yes, but.
If you eventually want batteries to run when grid is down, then it will need to go into the inverter that manages the battery.
Exactly... yes doable... but has implications as noted for code compliance, basic safety consideration (especially if main panel is indoors /locked space), and of course for future maintenance (or system updates, like adding a grid-forming hybrid inverter, to enable solar to work in grid-down situation, and add batteries).
So, yes you can... but don't. would be short-sighted (penny wise, pound-foolish) in most cases where it would be legal
My recent AC coupled micro-invertor system has a small sub-panel installed on the outside wall, near meter. The electrician was able to quickly and easily mount the small sub-panel, with not-bad cable routing/conduit (12") from main load center, including neat exit of main load center, out stucco into short section of external conduit.. routing panels inter-connection wiring in-wall would be nicer looking, but was, imo, too much to ask, and not necessary.
So if main load center is outdoor, next to meter, and not locked, such that basic safety considerations (first responder shutoff) met and local code allows such, I'd still argue the cost to add a sub-panel is minimal. The sub-panel itself is cheap, as is the extra breaker, and maybe an hour or two extra of electrician time?? with huge improvement to ease of future system maintenance and configuration flexibility (basic modularity).
It just seems that there are only a few situations where a homeowner would NOT regret the absence of using a sub-panel ...
