Counterattacks are part of a defence. A light Strike battalion (whatever that turns out to be once everyone finishes fiddling with it) is not the force to do that.
A combined arms battalion with Javelins and Stingers with some thermobarics, AT-4, armed UAVs and deep strike capability (by which I presume you are talking indirect fire support can do all that too AND can counterattack which your lighter force can't.
I think one has to keep in mind that the brigade has been and remains a "close combat" force. Its primary weapons operate within limited ranges unless you add manoeuvre. Even if you upgrade a CS artillery regiment's range capabilities, the deep battle it might participate in is not the BCT's battle but that of other formations assigned specifically to the deep battle. Some of those may be specialized forms of BCTs (such as the UK Deep Strike Brigade) others may be lay-behind special forces or satellite ISR systems or passive/active sensor systems directing deep strike missiles etc, etc. Quite frankly we don't know what shape those organizations will be yet. Just for the fun of it,
here's a fairly recent US publication about the Army's thoughts on BCT's Cross-domain Manoeuvre concepts. They see utility in all forms of BCTs and I'm sure as future weapon system mature these roles will be refined.
Let me add one thing. There's no such thing as a "light" airborne or "light" air mobile force. The delivered portion might be "light" but the delivery means are very heavy, very complex, tremendously expensive and very vulnerable. Without those delivery system you are not only "light" but also "practically static".
I've never argued that there isn't a role for the type of forces you and others suggest; I'm merely saying that the argument that one doesn't need heavy systems is a fallacy. It was a fallacy when we designed our Future Force in 2000-2003. We quickly learned in combat against a very unsophisticated but resourceful enemy that suddenly we needed to heavyize our force with modern precision artillery, tanks and much heavier double hulled LAVs that almost rank up there with IFVs.
Things are changing, yes they are, but things have been changing since the end of WW2 and there hasn't been a decade where some new weapon development hasn't resulted in a flurry of pundits announcing the death of the tank (and by association "heavy" forces) and yet they are still here and, at least in the
US Army's eyes, will be around for quite a while yet.