Once I have H2S/Oboe/Gee/Window etc. I'd equip every 4 engine heavy with it and use them to do them same. At night.
H2S and Gee were fitted to most bombers but they were navigation aids than bomb aimers. They weren't capable of precision attacks.
Oboe could only control 1 bomber at a time so was only useful for pathfinders or very small attacks. It also had a limited range.
IMHO Harris was aptly named the Butcher who harkens memories of Haig , why didn't he follow the plans laid out pre war for attacking POL
Oil was BC's number one target for some time in 1940 and 1941. It was abandoned as a target because experience showed attacks were having no effect. When Harris took command of BC in 1942 there was no question of him making oil a target again. He had to adhere to the priorities set out for him by his commanders.
the dummy couldn't or better yet would not transfer any 4 engine aircraft (long range) to protect convoys
Harris was head of BC, not Coastal Command. Allocation of resources to various commands was not part of his job, that was decided at a higher level.
Harris did, of course, expend major effort on minelaying. From 1,055 mines laid in 1941, BC greatly increased the effort under Harris with 9,574 laid in 1942, 13,834 in 1943.
The truth is BC didn't have the accuracy for large scale precision attacks until early 1944. They spent the first half of the year supporting the invasion, the second half of the year they carried out many precision attacks, day and night.
There isn't really much that could sensibly be changed with hindsight. The battle of Berlin was clearly a mistake, but apart from that, BC did pretty much the best it could with the technology that was available at the time.