Setting up a batch printing workflow

I'm going to define a printing workflow with C1 and there is a number of things I have to understand — I'm going to start with this post about the most important ones.

Before going on, let me shortly recap my previously experience with printing and my context (if you want to go straigthly to my C1 question, scroll down to 'MY QUESTION'):

Up to about 10 years ago I printed photos on my own with an Epson 2100 (and Lightroom). I got very good results, so I can say my knowledge and practical experience with screen calibration and paper colour profiles was ok. At a certain point I gave up because I wasn't often at home because of my job, so a long time passed between printing sessions and the printing nozzles unavoidably became clogged. Later I had a good experience with printing a book with Blurb and a partial experience with remote printing services. Then I didn't have time to dedicate to printing any longer.

Now I want to resume with printing, a thing I've never done with C1; so I'm re-evaluating all the available options:

1. Printing at home with a new “ecotank" printer, that seems to fix the nozzle clogging problem (furthermore I'm more often at home).
2. Printing photobooks with Blurb and similar services.
3. Printing single photos with printing services.

I'd like to go with option #1, but since it requires a considerable initial investment I'd like to try the other two approaches and figure out costs.

My constraints: 200/300 printed photos per year; with the exception of — say — 5% of special photos (typically hi-key/low-key ones), I don't want to post-process each one specifically for printing; so everything should work in batch.

The past week I've run a couple of attempts with printing services (that expect JPG or PNG files). I used export recipes (the “Print” menu seems not to offer anything more, with the exception of captions that at the moment I don't need). My approach is: tag print candidates with specific keywords that define the printing service and the kind of paper, then run a script; the required PNG files appear in specific folders, ready to be uploaded.

MY QUESTION

As expected, it turns out that, despite the colour profiles, I need to pre-process print candidates, most notably increasing brightness and decreasing colour temperature (this is consistent with my limited, previous experience with printing services and Lightroom). If memory doesn't fail me, Lightroom allowed to apply “incremental” settings (that is, if I had a photo post-processed with exposure +1, it allowed me to _add_ (not _set_) another amount, e.g. +0.5, so to have a final value of 1.5). C1 seems not to have such an option. Can you confirm?

The only two approaches I'm seeing are:

1. Use an external application (in batch mode) to apply fixes, using the "Open with" option in export recipes — I've already played with this approach e.g. to export to file formats not natively supported by C1; it's doable, but a bit cumbersome, especially on macOS.
2. Use a script that would create a special virtual copy, read current post-processing settings such as exposure and colour temperature, do the math for computing the final values, apply them and at last running the export recipe. Simpler than the previous option for some aspects, more complex for others, and with a couple of details that I need to understand.

Before proceeding I'd like to hear some feedback, in case somebody managed to do that with a simpler solution.