OK... three comments on this.
First, Bonaventure had actually just undergone a major refit (from 1967-68) that was intended to see her operate until at least 1978... if the decision had been made in 1964/65 to purchase A-4Es, then the needed changes would have been part of that refit.
Second, the Skyhawk Proposal document linked describes the 8,500 lb.s.t. J52-P-6 engine of the early A-4Es... very shortly they were fitted with 9,300 lb.s.t. J52-P-8 engines... and by 1968 the first A-4Ms were being built with 11,200 lb.s.t. J52-P-408 engines!
Third, the USN operated 4-aircraft units of A-4s from the ASW Essex-class modernized carriers (they still had hydraulic catapults, unlike the steam catapult-equipped Attack Essex-class modernized carriers) for "anti-snooper"/carrier-CAP duties... so that could have been a suitable role for detachments of RCAF A-4Es... easily upgrade-able to a full fighter/attack air wing if necessary.
To improve the situation, there had already been an A-4 tested with an air-air radar in 1965... "Rudolph"!
http://www.ebdir.net/vsf1/boom_powell_part_1.html
Rudolf was an A-4B (BuNo 145002) that had an F-8 air-to-air radar "borrowed" from the China Lake Weapons Center and installed by NARF Alameda sometime in 1965. The unique, longer nose (modified from a F-11 Tiger) was painted red and the name followed soon after.
What was intended as the prototype for future VSF fighters had not been approved by higher authority. Nor was taking Rudolf on the CarQual sessions the pilots of VSF-1 had on Kearsarge and Hornet.
VSF-1 commanding officer CDR Charles E. Waring himself flew Rudolf's first trap. Six pilots and the maintenance crew of the first detachment were ready to go aboard Yorktown when the deployment was cancelled in the spring of 1966.
That radar was likely from an early-model F-8... the radar in the F-8D or F-8E would have been a better choice for a production aircraft... and if fitted with the AIM-9D IR-guided missile and the AIM-9C radar-guided missile could have been very useful!
http://www.designation-systems.info/dusrm/m-9.html
The AAM-N-7 Sidewinder IC was developed in two version: a semi-active radar homing version (called Sidewinder IB in source [1]), designated AIM-9C in 1963, and an IR guided version, later designated as AIM-9D. Improvements common to both IC versions include a new Hercules MK 36 solid-fuel rocket motor for significantly increased speed and 18 km (9.7 nm) range, a larger MK 48 continuous-rod warhead, and slightly larger fins.
The SARH AIM-9C was only used with the Navy'S F8U Crusader fighters to provide these with an all-weather capability without having to fit a Sparrow-compatible radar. However, the AIM-9C was not very successful, and only 1000 were built by Motorola between 1965 and 1967.
So by the time Bonnie came out of her "mid-life refit" she could have had A-A radar-equipped A-4ECs* with 11,200 lb thrust engines and radar-guided A-A missiles!
* Better would have been A-4MCs with the larger raised cockpit of the A-4M that granted better all-round visibility for the pilot (important for a fighter), as well as my proposed radar & missile outfit.
Aaahhh... what could have been!