How practical is to use this for a OLTP DB engine?

[mamcx]

The idea of reusing building blocks is appealing, unfortunately most I see is only from OLAP-like workloads.

I have in mind an engine that is a mix of both, but biased to OLTP for use in normal erp-like apps.

Is there any experiment related to this? how much of a penalty is there?

P.D: I well aware of the distinctions in workloads and have worked as part of a commercial DB engine, so what I asking is not about the basics, instead, is (assuming all other things are made right), how much of a penalty is there.

If for example the answer is like "median 4x" but the speed could in theory make possible go faster than PG, then it could be a good idea.