Bat guano yes you can but no you shouldnt

You will still need to use a coco base fertiliser or similar

Mix some into your coco and have a patch at the top which has no guano in so you don't burn the seedling and when the roots actually get to the guano she will use that for roots n shoots..

if you are treating the coco like a soil, sure, why not. If you are treating it as a soilless medium, then no, you should not. coco has no nutrients, so you need to provide a full diet one way or another... there's more than one way to skin that cat. Sounds like you want to run a soil grow, so you should buy a soil or make a soil etc. that can include coco coir, of course, but it needs more than that. in a soilless/hydro context, a 70/30 coco+perlite medium is fine. I''d recommend Promix hp or bx with 50% vermiculite as an alternative that is likely better. Soilless hydro is a no-brainer. you provide a steady complete diet each irrigation with 10% runoff waste out the bottom, which prevents buildup in the medium. Easy-peasy. No adding shit to the medium, no playing mad scientiest adding this or that here or there... Mixing these methods comes with zero synergy and likely negatives. I can't help with making a soil from scratch, but there are probably a shit-ton of guides out there for that. I'd probably only suggest that you use a 50:50 mix of perlite or vermiculite for a high-water capacity medium for propery aeration and drainage properties. If it's just coco, it holds less water and that;s why it's ~33% in that context. Again, 30% or 33% is not something to get nitpicky about. Recipes that suggest less of this type of amendment per volume are less ideal for roots - not debatable, just a fact.