variable cycle engines will be few years away for J-36/J-50 most probably they will come after 2032-35, and Lasers is for defense for your jet rather than offensive weapons like disabling opponent air to air missiles at short ranges/electronic countermeasures and ECCM purpose (unfortunately lasers could not work very well at long and medium ranges)
And as for 1000 km+ BVRs are also not Feasible in near future because of curvature of Earth which is limited by radar range all fighter jets including 5th and upcoming 6th gen jets radar ranges are limited by earth this physical parameter/barrier, and at 400 km fighter jets are only able to detect, for tracking and engagements targets needs to become much closer, I know some AWACS are capable to detect targets over 600 km like E-2D but it can detect BOMBERS/tankers and other big RCS slow moving ISR targets at this range (I only say they can only detect not attack those targets at 600 km) and also they uses UHF (Short range radio waves) bands to detect those targets at 600 km range which insufficient for engaging/ tracking, if you want to engage fighter jets or other big targets you needs X band which has much shorter range than UHF band like 200/250/300 km, so assuming that China will built 1000 km+ BVR in near future is wishful thinking