The first module I engineered with him only gave me 1 level and 10% on grade 2.
Sorry, I should have been clearer: the first module you engineer
to near the top of grade 4 or higher will max your rep anyway.
But as the main use of maxed rep is to be able to engineer grade 5 modules, and you need a grade 4 module anyway to be able to engineer a grade 5 module, there's no way that your rank with him can be
behind the module pre-requisite except in very unusual circumstances (you've brought him a module that someone else has started off, for example) - your rank always increases faster than the module itself does.
For Tod where the 5M bounties to max him out are readily obtainable anyway it's fine either way; some of the others are a
lot quicker to rank up just by engineering a module through the various grades than they are to use the alternative route (and some of the others don't have any alternative routes at all, of course)
(They should get rid of engineer rank - the Odyssey ones don't have it and it's not a problem - it's a leftover from a much earlier design and it just overcomplicates things nowadays. But that's probably not something they'll have time for)