Sure, it could be added, but there are much better choices for an early war RAF bomber. Luftwaffe fans often try to equate the Blenheim to the Ju88 or He111, but the fact is that it was not the RAF's equivalent of those. That would be the Wellington, which would be an excellent addition as an early war bomber that early war fighters could actually catch, yet being durable enough and with a large enough war load as to be worth using.
indeed, the Blenheim much like the Hampden would not be very competitive even in EW scenarios. the Beaufort might be interesting, but the upcoming (
) Beaufighter will be more versatile.
the Buckingham would be a useful and interesting addition (340mph, 2000fpm, 4000lb ords, 4x front, 4x dorsal and 2x ventral .303s) but was produced in very limited numbers